Biology Part A - Rivera Early College High School...Brownsville Independent School District 1900 Price Road, Brownsville, TX 78521, (956) 548-8000 Mayo de 2020 Estimados Padres y Miembros

Biology

Student Name: __________________

Student ID: _____________________

School Name: ___________________

Summer School Distance

Learning Packet

Teacher Name: __________________

HIGH SCHOOL

Part A

Brownsville Independent School District

1900 Price Road, Brownsville, TX 78521, (956) 548-8000 www.bisd.us

May 2020

Esteemed Parents and Family Members,

We hope this letter finds you safe and healthy amid this uneasy time of COVID-19. As always, our priority is

the safety and welfare of our students. Our 2020 summer program will continue by utilizing virtual learning

platforms and will begin on June 1 and end on June 18, 2020. The purpose of the summer program is to

provide students the opportunity to gain credit for the course your student has failed.

You have received this summer 2020 instructional packet for your (9th - 12th grade) student. This instructional

packet includes materials for the core area(s) your student has failed.

We ask that you contact your student’s school to:

• give you the failing subject area(s)

• give you your student’s summer teachers’ name and contact information / email address

• update any contact information including any changes and additional contact numbers, and

email addresses, etc.

• receive login information for the digital platform

The platform utilized this summer will be:

• 9th -12th Google Classroom

(Download Google Classroom app or access through the Clever Portal)

Our sincere hope is that your child will participate and take advantage of this opportunity for promotion that

will greatly support your child’s area(s) of educational need.

Please encourage your student to read, watch educational programs, and practice their writing and speaking

skills. This is also a great time to share family stories and traditions, play board games and enjoy family time.

As always, it is an honor to continue to serve you and we value your family's commitment in entrusting us with

your child's education.

BISD does not discriminate on the basis of race, color, national origin, gender, religion, age, or disability or genetic information in employment

or provision of services, programs, or activities.

Brownsville Independent School District

1900 Price Road, Brownsville, TX 78521, (956) 548-8000 www.bisd.us

Mayo de 2020

Estimados Padres y Miembros de Familia,

Esperamos que esta carta le encuentre a buen resguardo y en buena salud durante estos días difíciles del

COVID-19. Como siempre, nuestra prioridad es la seguridad y el bienestar de nuestros estudiantes. Nuestro

programa de verano 2020 continuará utilizando plataformas de aprendizaje virtuales y comenzará el 1 de junio

y terminará el 18 de junio de 2020. El propósito del programa de verano es proporcionar a los estudiantes que

no fueron promovidos al siguiente grado, una oportunidad para obtener la promoción.

Con el fin de trabajar en la promoción de su hijo/a al siguiente grado, usted ha recibido un paquete de

instrucción para el verano del 2020 para su hijo/a de preparatoria. Dicho paquete incluye materiales para la(s)

asignatura(s) que su hijo/a reprobó.

Le pedimos que se ponga en contacto con la escuela de su hijo/a para:

• darle el área(s) de materia(s) que está reprobando.

• darle el nombre del maestro/a de verano de su hijo/a y su correo electrónico

• actualizar cualquier información de contacto, incluyendo cualquier cambio y números

de contacto adicionales, y correo electrónico, etc.

• recibir la información para conectarse a las plataformas digitales

La siguiente plataforma virtual se utilizará este verano para la preparatoria:

• Google Classroom

(Descargar aplicación de Google Classroom o usar el portal de Clever)

Esperamos sinceramente que su hijo/a participe y aproveche esta oportunidad de promoción que apoyará en

gran medida las áreas de su necesidad educativa.

Anime a sus hijos/as a leer, ver programas educativos y practicar sus habilidades para escribir y hablar. Este es

también un gran momento para compartir historias y tradiciones familiares, jugar juegos de mesa y disfrutar

del tiempo en familia.

Como siempre, es un honor continuar sirviéndole y valoramos nuestro compromiso con su familia al

confiarnos la educación de su hijo/a.

BISD no discrimina de acuerdo de raza, color, origen nacional, género, religión, edad, información genética, o incapacidad en el empleo o en

la provisión de servicios, programas o actividades.

Biology Part A- Summer 2020 Curriculum

Lesson Concepts TEKS Assignments

Week 1: June 1-5

1

Biomolecules

9A -2.3 Carbon Based Molecules Interactive Reader Pgs. 28-32 -Section 3 Study Guide A Pgs. 1-2

2

Cells & Transport

4AB

-3.1 Cell Theory Interactive Reader Pgs. 40-41 -Section 1 Study Guide A Pgs. 1-2

3

-3.4 Diffusion & Osmosis Interactive Reader Pgs. 49-51 -Active Reading: Homeostasis & Cell Transport Pgs. 2-3

VISUALVOCAB

seCTion

2.3

Carbonatomshaveuniquebondingproperties.Most molecules that make up living things are based on carbon atoms. The structure of a carbon atom allows it to form up to four covalent bonds. It can bond to other carbons or to different atoms. As shown in the figure below, carbon-based molecules have three basic structures: straight chains, branched chains, and rings.

CARBonCHAinSAndRingS

Straight chain

A simplified structure can also be shown as:

branched chain Ring

Each line represents a covalent bond. Each letter represents an atom. Notice that there are four bonds for every carbon atom (C). When a carbon (C) is attached to a hydrogen (H) sometimes there is no line drawn to represent the bond, but the bond is still there.

CH3 CH

CH2

CH2 CH3

CH3

CH3 CH2 CH2 CH CH2

C C C C C

H H H H H

H H H H

H

OC

C

C

OH

CH

CH

CH

CH

O

CH3

Think of a chain made up of connected loops, or links. Each link is a subunit that makes up the bigger chain. Many carbon-based molecules have subunits that make up a bigger molecule.

Each subunit is called a monomer. When monomers are linked together, they form molecules called polymers. A polymer is a large molecule made of many monomers bonded together. A polymer can also be called a macro-mole-cule. Macro- means “large,” so a macromolecule is a large molecule. The monomers that make up a polymer can all be the same, or they can be different, depending on the type of macromolecule.

How are polymers and monomers related?

Carbon-Based MoleculesKEyConCEPT carbon-based molecules are the foundation of life.

each smaller molecule is a subunit called a monomer.

A polymer is a molecule that contains many monomers bonded together.

monomer

polymer

mono- = onepoly- = many

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28 Holt McDougal Biology

9A

DO NOT EDIT--Changes must be made through “File info” CorrectionKey=A

fourmaintypesofcarbon-basedmoleculesarefoundinlivingthings.

All organisms are made of four types of carbon-based molecules: carbohydrates, lipids, proteins, and nucleic acids.

CarbohydratesFruits and grains both contain large amounts of carbohy-drates. Carbohydrates are molecules made of carbon, hydro-gen, and oxygen. Sugars and starches are both types of carbo-hydrates. These carbohydrates can be broken down to produce energy in cells. Some carbohydrates are part of cell structure in plants.

The most basic carbohydrates are simple sugars. Many simple sugars have five or six carbon atoms. Fructose and glucose are both sugars that have six carbon atoms. The sugar that you might use in the kitchen is made of two sugar molecules bonded together.

Many glucose molecules bonded together form polymers such as starch and cellulose. These polymers are called polysaccha-rides. Starches are carbohydrates made by plants. Starch can be broken down as a source of energy by plant and animal cells. Cellulose is also made by plants. Cellulose makes up cell walls, the tough outer covering of plant cells. The stringy fibers of vegeta-bles like celery are made of cellulose. The structure of starch molecules is different from the structure of cellulose molecules. The different structures give them their different properties.

CARBoHydRATESTRUCTURE

Polymer (cellulose)Cellulose is a polymer of glucose monomers that has a straight, rigid structure.

monomer

Polymer (starch)

Starch is a polymer of glucose monomers that often has a branched structure.

monomer

Poly- means “many.” Sac-charide means “sugar.” A polysaccharide is a poly-mer made of many sugars.

VoCABULARy

CH2OH

H

H H

HHOH

OH

OH

OC

HO

C

C C

C

Glucose is a six-carbon sugar. Glucose is often represented by a hexagon, a six-sided figure. Each point on the hexagon represents a carbon, except the point that has an O, for oxygen.

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29Interactive Reader


LipidsLipids are molecules that include fats, oils, and cholesterol. Lipids are nonpolar, so they do not dissolve in water. Like carbohydrates, most lipids are made of carbon, oxygen, and hydrogen atoms. Some lipids are broken down and used as energy in cells. Other lipids form part of the cell’s structure.

Fats and lipids store large amounts of energy in organisms. Animal fats are found in foods such as meat and butter. Plant fats are found in nuts and oils, like olive oil or peanut oil. Fats and lipids are made of molecules called fatty acids. Fatty acids are chains of carbon atoms bonded to hydrogen atoms. In many lipids, the fatty acid chains are attached on one end to another molecule called glycerol. Because of the shape of the fatty acid chains, some fats are liquid at room temperature, like olive oil, and other fats are solid, like butter.

All cell membranes are made mostly of another type of lipid, called a phospholipid (fahs-foh-LIHP-ihd). A phospholipid has glycerol, two fatty acid “tails,” and a phosphate group that forms the “head” of the molecule. The phosphate group includes phosphorous and oxygen atoms. This part of the molecule is polar, so it is attracted to water. The fatty acid end of the molecule is nonpolar, and is not attracted to water.

Cholesterol (kuh-LEHS-tuh-rawl) is a lipid with a ring structure. Although high cholesterol is a health risk, your body needs a certain amount of cholesterol to function. Cholesterol is part of cell membranes. Cholesterol is also an important part of steroid hormones. Cholesterol-based steroids help your body respond to stress and also control sexual development and the reproductive system.

ProteinsProteins are the most varied of the carbon-based molecules in organisms. There are many different types of proteins. They are involved in many different body functions including movement, eyesight, and digestion.

fATTyACidS

O

CH2HOC

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH3

Fatty acid

Fatty acids are long chains of carbon atoms attached to hydrogen atoms.

PHoSPHoLiPidSTRUCTURE

Phospholipid A phospholipid has nonpolar fatty acid “tails” and a polar “head” that contains a phos-phate group.head tails

Po4–

butter is made up of fatty acids.

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Holt McDougal Biology30


A protein is a polymer made of monomers called amino acids. Amino acids are molecules that contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Organisms use 20 different amino acids to build different types of proteins. Your body can make 12 of the amino acids it needs. The other 8 amino acids come from the foods you eat, such as meat, beans, and nuts.

Look at the figure at right to see the amino acid called serine. All amino acids have part of their structure that is the same. Another part of their structure is different for each amino acid. The part that is different is called the side group, or R-group. Amino acids are bonded together to form proteins.

AminoACidAndPRoTEinSTRUCTURE

All amino acids have a carbon atom bonded to a hydrogen atom, an amino group (NH2), and a car-boxyl group (cooH). Different amino acids have different side groups (R).

Monomer (amino acid)

Peptide bonds form between the amino group of one amino acid and the carboxyl group of another amino acid.

Polymer (protein)

A polypeptide is a chain of precisely ordered amino acids linked by peptide bonds. A pro-tein is made of one or more polypeptides.

peptide bondsH

C

H

R

N NC

O

H

C

O

peptide bonds

H

C

O

OH

C

R

N

H

H

Proteins are different based on the number and order of amino acids. A protein’s function depends on the specific order of the amino acids, which affects the shape of the protein. The side groups of each amino acid can interact with each other and affect the protein’s shape. For example, hydrogen bonds can form between different side groups.

Hemoglobin is the protein in your red blood cells that transports oxygen. Hemoglobin is made of 574 amino acids. Hydrogen bonds help make the structure of this protein. If just one of the amino acids in hemoglobin changes, the structure of the protein can change in a way that prevents the protein from working properly. A change in one amino acid in hemoglobin causes the disorder called sickle cell anemia.

nucleicAcidsThere are two general types of nucleic acids: DNA and RNA. Nucleic acids are polymers that are made up of monomers called nucle-otides. A nucleotide is made up of a sugar, a phosphate group, and a nitrogen-containing molecule called a base. Nucleic acids contain the instructions to build proteins.

H

C

O

OH

C

CH2

N

H

H

oH

This part is different for each amino acid monomer.

This part is the same for each amino acid monomer.

Typically, red blood cells are shaped like a saucer (left). A change in just one amino acid in hemoglobin can cause cells to have the curved shape characteristic of sickle cell anemia.©

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Nucleic acids are different from the other three macromolecules you read about. Carbohydrates, lipids, and proteins have many different structures and functions. Nucleic acids have just one function. They code for proteins. You will learn more about nucleic acids in Unit 3.

What are four main types of macromolecules found in living things?

monomer protein

polymer amino acid

carbohydrate lipid

fatty acid nucleic acid

1. Name four types of macromolecules.

2. A protein is made up of monomers called .

3. The carbon chain that makes up part of a lipid is called a .

4. A six-carbon sugar is an example of a that can join with other molecules to form a such as starch or cellulose.

1. What are three different shapes, or structures, of carbon-based molecules?

2. Complete the following chart.

monomER PoLymER ExAmPLE fUnCTion

Glucose

Protein

DNA

3. What is a phospholipid?

4.Living things are sometimes called “carbon-based life forms.” Do you think this is a good way to describe life? Explain your answer.

2.3 VocabularyCheck

Go back and highlight each sentence that has a vocabulary word in bold.

Mark It Up

2.3 TheBigPicture

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Name ______________________________ Class ___________________ Date __________________

© Houghton Mifflin Harcourt Publishing Company

Holt McDougal Biology 1 Chemistry of Life

Section 3: Carbon-Based Molecules

Study Guide A KEY CONCEPT Carbon-based molecules are the foundation of life.

VOCABULARY

MAIN IDEA: Carbon atoms have unique bonding properties.

Choose whether the statement is true or false.

1. true / false Carbon atoms form the building blocks of most living things.

2. true / false Carbon’s outer energy level is full.

3. true / false Carbon atoms can form covalent bonds with up to four other atoms.

4. true / false The three basic structures of carbon-based molecules are straight chain, bent chain, and ring.

5. Choose one of the three basic structures of carbon-based molecules to sketch in the space below. Label your sketch with the name of the basic structure.

monomer lipid amino acid polymer fatty acid nucleic acid carbohydrate protein

Name ______________________________ Class ___________________ Date __________________


Holt McDougal Biology 2 Chemistry of Life

Study Guide A continued

MAIN IDEA: Four main types of carbon-based molecules are found in living things. Complete the table with the functions and examples provided for each type of carbon-based molecule.

Vocabulary Check 14. The prefix mono- means “one,” and the prefix poly- means “many.”

Which contains more molecules, a monomer or a polymer? _____________________

Functions Examples Provide energy meat fat oils Building blocks of proteins sugar beans DNA Map for making proteins RNA starches nuts Store energy

Molecule Type Functions Examples

Carbohydrate 6. 7.

Lipid 8. 9.

Protein 10. 11.

Nucleic acid 12. 13.

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sECTiOn

3.1Earlystudiesledtothedevelopmentofthecelltheory.

Cells are the very smallest parts of life. All living things are made of cells. However, most cells cannot be seen without a microscope. How did scientists find out about cells when they couldn’t see them?

DiscoveryofCellsOver many years, many scientists observed and studied cells under the microscope. As early scientists improved both microscopes and lenses, they could learn more and more about cells. Some of these findings are listed in the table below.

SCiEnTiST(YEAR) FinDing

hooke(1665) identified and named cells

Leeuwenhoek(1674) observed living cells; could see greater detail due to better lenses

schleiden(1838) noted that plants are made of cells

schwann(1839) concluded that all living things are made of cells

Virchow(1855) proposed that all cells come from other cells

CellTheoryThe discoveries of these early scientists came together into the cell theory. Today’s scientists agree with this cell theory. It says three things:

• All living things are made of cells.• All cells come from other living cells.• The cell is the most basic unit of life. There is nothing living

that is smaller than a cell.

Underline the part of the cell theory that says where cells come from.

Cell TheoryKEYConCEPT Cells are the basic unit of life.


3F, 4A


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Prokaryoticcellslackanucleusandmostinternalstructuresofeukaryoticcells.

Cells come in different shapes and carry out different jobs. However, they all share some features. Cells are very small. They are surrounded by a membrane that controls what enters and leaves the cell. They have cytoplasm, a jellylike material that contains the building blocks needed for life. And they are made of similar molecules. One of these mol-ecules is DNA, the genetic information.

There are two main types of cells, prokaryotic cells and eukaryotic cells. Prokaryotic cells are extremely small. Their DNA floats in the cytoplasm, and they have no distinct* internal parts. Prokaryotes, such as bacteria, are made of only one cell. Eukaryotic cells have a nucleus, which is a mem-brane that separates DNA from the cytoplasm. The nucleus is a type of organelle, a small part that carries out a specific job in a cell. Eukaryotic cells have many types of organelles. Like the nucleus, most organelles are covered by a membrane. Eukaryotes, such as plants and animals, are made of one cell or many cells.

In the text above, circle two things that eukaryotic cells have inside them that prokaryotic cells do not have.

* ACAdemIC VoCAbUlAry

distinct distinguishable as a separate entity

cell theory eukaryotic cells

cytoplasm organelle

prokaryotic cells

1. Name two types of cells. ,

2. In both types of cells, the jellylike substance is .

3. Parts that carry out specific jobs within a cell are .

4. List the three parts of the cell theory.

3.1 VocabularyCheck


Mark It Up

3.1 TheBigPicture

Prokaryoticcells do not have a nucleus or other membrane-bound organelles.

VISUALVOCAB

cell membrane

nucleus organelle

cytoplasm

Eukaryoticcells have a nucleus and other membrane-bound organelles.

dNA



Name ______________________________ Class ___________________ Date __________________


Holt McDougal Biology 1 Cell Structure and Function

Section 1: Cell Theory

Study Guide A KEY CONCEPT Cells are the basic unit of life.

VOCABULARY

MAIN IDEA: Early studies led to the development of the cell theory. Match each scientist in the table with the statement listed below that describes what he did to help develop the cell theory.

a. concluded that animals and, in fact, all living things are made of cells.

b. was the first to identify cells and name them.

c. proposed that all cells come from other cells.

d. concluded that plants are made of cells.

e. observed live cells and observed greater detail.

cell theory organelle eukaryotic cell cytoplasm prokaryotic cell

Scientist Letter of Statement that Completes the Sentence

1. Hooke

2. Leeunwenhoek

3. Schleiden

4. Schwann

5. Virchow

Name ______________________________ Class ___________________ Date __________________


Holt McDougal Biology 2 Cell Structure and Function


Circle the word that best completes the statement about cell theory.

6. The cell theory states that: i. All organisms are made of organelles / cells. ii. All existing cells are produced by other living / dead cells. iii. The atom / cell is the most basic unit of life.

7. Cell theory is one of the great unifying theories of biology / chemistry.

MAIN IDEA: Prokaryotic cells lack a nucleus and most internal structures of eukaryotic cells.

8. For each of the following cell characteristics, place a check mark in the appropriate box or boxes to indicate whether it is a characteristic of eukaryotic cells, prokaryotic cells, or both.

Vocabulary Check Fill in the blank with the word or phrase that best completes the sentence.

9. The jellylike substance that contains dissolved molecular building blocks and, in some types of cells, organelles, is called ______________________.

10. ______________________ cells have no nucleus.

Characteristic Eukaryotic cells

Prokaryotic cells

Surrounded by a cell membrane

Contains cytoplasm

Contains a nucleus

Contains membrane-bound organelles

Tends to be microscopic in size

Either single-celled or multicellular

Only single-celled

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* ACAdemIC VoCAbUlAry

gradient a slope or incline; the change in a quantity per unit distance

Passive transport is the move-ment of molecules across the membrane from areas of higher concentration to areas of lower concentration. It does not require energy input from the cell.

outside inside

Diffusion and OsmosisKEYConCEPT materials move across membranes because of concentration differences.

Diffusionandosmosisaretypesofpassivetransport.

Cells are constantly taking in and sending out substances. But cells do not have to use energy to move all those molecules. Passive transport is the movement (transport) of molecules without a cell using energy (passive).

ConcentrationConcentration is the amount of molecules of one type in an area. If there are few molecules, the area has a low concentration. If there are many molecules, the area has a high concentration. Concentra-tion can vary from one region to another. A concentration gradient is the difference in the concentration of a substance from one location to another. Molecules move from one place to another because of this difference in concentration.

Diffusion is the movement of molecules from a place of higher concentration to a place of lower concentration. When molecules diffuse, they are described as moving down their concentration gradient*. The diffusion of molecules across the cell membrane is a type of passive transport. It happens because of the natural motion of particles. Diffusion does not need energy from a cell.

The diffusion of water molecules is called osmosis. The process of osmosis is exactly the same as diffusion but refers only to water mol-ecules. Water molecules diffuse across a membrane from a place of higher water concentration to a place of lower water concentration.

SolutionsIf you dissolve salt in water, you have made a solution. The more salt you put in the water, the higher the concentration of salt becomes, and the lower the concentration of water becomes. The salt is the solute, and the water is the solvent.

Cells are usually surrounded by fluid. The type of solution that a cell is in can have a big effect on the cell. There are three types of solutions: isotonic, hypotonic, and hypertonic. These terms are comparisons. They compare the concentration of one solution to the concentration of another solution.

sECTiOn

3.4


4B, 9A


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• A solution is isotonic to a cell if it has the same concentration of solutes that the cell has. Iso- means “equal.” In an isotonic solution, water moves into and out of a cell at equal rates. As a result, cell size remains constant.

• A solution is hypertonic if it has a higher concentration of solutes than a cell. Hyper- means “more.” This means the cell has a higher concentration of water than the surrounding fluid. As a result, water diffuses out of the cell, and the cell shrivels.

• A solution is hypotonic if it has a lower concentration of solutes than a cell. Hypo- means “less.” This means the cell has a lower concentration of water than the surrounding fluid. As a result, water diffuses into the cell, and the cell grows larger.

Notice how water moves from the area of higher water concentration to the area of lower water concentration in two of the pictures below.

EFFECTSoFoSmoSiS

iSoToniCSoLUTion

A solution is isotonic to a cell if it has the same concentration of solutes as the cell. equal amounts of water enter and exit the cell, so its size stays constant.

HYPERToniCSoLUTion

A hypertonic solution has more solute than a cell. overall, more water exits a cell that is in a hyper-tonic solution, causing the cell to shrivel or even die.

2 HYPoToniCSoLUTion

A hypotonic solution has less solute than a cell. overall, more water enters a cell that is in a hypotonic solution, causing the cell to expand or even burst.

hypertonic

31

osmosisisthediffusionofwateracrossasemipermeablemembranefromanareaofhigherwaterconcentrationtoanareaoflowerwaterconcentration.

isotonic

isotonic hypotonic

hypertonic hypotonic

In each picture above, mark a plus () where the water con-centration is higher, and a minus () where it is lower.



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Facilitated diffusion enables molecules that cannot directly cross the phospholipid bilayer to diffuse through transport proteins in the membrane.

outside insideSomemoleculesdiffusethroughselectivetransportproteins.

If some molecules can’t diffuse through the cell membrane by themselves, they can get help. Transport proteins give them a ride through the membrane. This process is called facilitated diffusion. The word facilitate means “to make easier.” Different transport proteins make it easier for certain molecules to get through the cell membrane without a cell using energy. Facilitated diffusion is another type of passive transport.

In facilitated diffusion, do molecules move down their concentration gradient? explain.

passive transport isotonic

concentration gradient hypertonic

diffusion hypotonic

osmosis facilitated diffusion

1. Which two words mean nearly the same thing?

2. Which word includes a “helper?”

3. Which word describes a slope?

4. How does passive transport benefit a cell?

5. Why do cells need facilitated diffusion?

6. Why does a cell swell in a hypotonic solution?

3.4 VocabularyCheck


Mark It Up

3.4 TheBigPicture



Name ______________________________ Class __________________ Date __________________

© Houghton Mifflin Harcourt Publishing Company Holt McDougal Biology 2 Cell Structure and Function

ACTIVE READING WORKSHEETS

HOMEOSTASIS AND CELL TRANSPORT

Passive Transport

Read the passage below, which covers topics from your textbook. Answer the questions that follow.

One type of passive transport is called facilitated diffusion. This process is used for molecules that cannot readily diffuse through cell membranes, even when there is a concentration gradient across the membrane. Such molecules may not be soluble in lipids, or they may be too large to pass through the pores in the membrane. In facilitated diffusion, the movement of these kinds of molecules across the cell membrane is assisted by specific proteins in the membrane. These proteins are known as carrier proteins.

In facilitated diffusion, a carrier protein binds to a specific molecule it transports. As soon as the molecule binds to the carrier protein, the carrier protein changes shape. This altered shape may shield the molecule from the hydrophobic interior of the lipid bilayer. Once shielded, the molecule can be transported across the cell membrane. On the other side of the membrane, the molecule is released from the carrier protein, which then returns to its original shape.

Read each question and write your answer in the space provided.

SKILL: Sequencing Information 1. Order the statements to show the steps of facilitated diffusion. Write “1” on the line in

front of the statement that describes what happens first. Write “2” on the line in front of the statement that describes what happens next, and so on. a. _____ The molecule is released from the carrier protein. b. _____ The carrier protein changes shape. c. _____ The molecule is transported across the cell membrane. d. _____ The molecule binds to a carrier protein. e. _____ The carrier protein returns to its original shape. f. _____ The molecule is shielded from the hydrophobic interior of the lipid bilayer.

Name ______________________________ Class __________________ Date __________________

© Houghton Mifflin Harcourt Publishing Company Holt McDougal Biology 3 Cell Structure and Function

2. In order of occurrence, briefly describe what happens in each of the three main parts of facilitated diffusion. a. _____________________________________________________________ b. _____________________________________________________________ _____________________________________________________________ c. _____________________________________________________________

Write your answer in the space provided.

SKILL: Vocabulary Development

3. The term diffusion comes from a Latin word meaning “to spread apart.” How is the term diffusion related to its Latin word of origin?

Circle the letter of the phrase that best answers the question.

4. What types of molecules diffuse through the cell membrane by facilitated diffusion? a. molecules that are not soluble in lipids b. molecules that are too large to pass through pores in the membrane c. molecules that can survive the hydrophobic interior of the lipid bilayer d. both (a) and (b)



Week 2: June 8-12

4

Cell Cycle & Cancer

5AC

-5.1 Cell Cycle Interactive Reader Pgs. 77-79 -Active Reading: Cell Reproduction Pgs. 1-2

5

-5.2 Mitosis & Cytokinesis Interactive Reader Pgs. 80-82 -Active Reading: Regulation of Cell Cycle Pg. 3

6 DNA

6AB -8.2 Structure of DNA Interactive Reader Pgs. 129-131 -Section 2 Study Guide A Pgs. 1-2

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The Cell CycleKEyConCEPT Cells have distinct phases of growth, reproduction, and normal functions.

seCtion

5.1Thecellcyclehasfourmainstages.

Cells grow and divide in a regular pattern, or cycle*. If you cut your finger, your cells grow and divide to make more cells. This is how your finger heals.

The cell cycle is a regular pattern of growth, DNA duplication*, and cell division* that occurs in eukaryotic cells. Recall that your cells are eukaryotic cells, and they have a nucleus. There are four main stages of the cell cycle:

• gap 1—normal growth• synthesis—DNA is copied• gap 2—more growth• mitosis—nuclear division

Each stage is described below.

Gap 1 (G1) In G1 cells do their normal functions. For example, your muscle cells contract, and intestinal cells absorb nutrients.

synthesis (s) Synthesis means “the combining of parts to make a whole.” During the S stage, a cell puts together, or synthesizes, a whole copy of its nuclear DNA. In eukaryotes, DNA is in the nucleus. At the end of this stage, there are two complete sets of DNA in a cell’s nucleus.

Gap 2 (G2) In G2 cells grow and continue their normal func-tions. If the cell is healthy, it will continue to the next stage.

Mitosis (M) There are two parts of this stage: mitosis and cytokinesis. Mitosis (my-TOH-sihs) is the division of the cell nucleus and the DNA inside it. Cytokinesis (sy-toh-kuh-NEE-sihs) is the division of the contents of the rest of the cell—the cytoplasm.

These four main stages are shown in the graph at the top of page 75.

* ACAdemiC VOCABulARy

cycle a pattern of events that is repeated

duplication the process of doubling, or copying

division separating

Mitosis is the division of the cell nucleus and its contents.

VISUAL VOCAB

Cytokinesis divides the cell cytoplasm.

parent cell

mitosis

cytokinesis

daughter cells

Daughter cells is a term to describe these resulting cells, but it does not mean that they are female.

Together, these three stages make up a part of the cell cycle called interphase.


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On the figure above, circle the terms for the four stages of the cell cycle.

Cellsdivideatdifferentrates.Different types of eukaryotic cells take different amounts of time to go through the cell cycle. The table at right lists the life span—or how long until a cell dies—for different types of human cells. Also, cells divide at different rates depending on a person’s age. Children’s cells divide faster than do cells in adults. In adults, many cells divide only if there is an injury or cell death.

How long does it take for a cell to go through the cell cycle?

Cellsizeislimited.A cell must be big enough to fit all of the mol ecules and organelles it needs to live. A cell also must be small enough to quickly transport nutrients and wastes into and out of the cell across the cell membrane. As a cell gets bigger, its volume* increases faster than its surface area*. If a cell gets too big, there is not enough surface area of the cell membrane to transport nutrients and wastes for such a big volume. The upper limit on cell size depends on its surface area-to-volume ratio. The surface area-to-volume ratio is the size of the surface area compared to the size of the volume.

CElllifEsPAn

CeLL tyPe aPProxiMate Life sPan

Skin cell 2 weeks

Red blood cell 4 months

liver cell 300–500 days

intestine—internal lining 4–5 days

intestine—muscle and other tissues

16 years

This chart shows the life span of five different types of human cells. Each type of cell divides at a different rate.

Cells grow and copy their DNA during interphase. During M stage, both the nucleus (in mitosis) and cytoplasm (in cytokinesis) are divided.

Gap 1 (G1) Cells grow, carry out normal functions,

and replicate their organelles.

Synthesis (S) DNA synthesis Gap 2 (G2)

Additional growth

Mitosis (M) Cell division

INTERPHASE

CYTOKINESIS

MIT

OSI

S

Prophase

Metaphase

Anaphase

Telophase


volume the amount of space in a three-dimensional object

surfacearea the total amount of area on the surfaces of an object



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RATioofsuRfACEAREAToVoluMEinCElls

Asacellgrows,itsvolumeincreasesmorerapidlythandoesitssurfacearea.

relative size

surface area (length 3 width 3 number of sides) 6 24 54

Volume (length 3 width 3 height) 1 8 27

ratio of surface area to volume 6 _ 1 = 6:1 24

__ 8 = 3:1 54

__ 27 = 2:1

1 32

Can a cell get too big? explain.

cell cycle cytokinesis

mitosis

Fill in the blanks with the correct term from the list above.

1. is the division of the nucleus and its contents.

2. The is a pattern of growth, DNA duplication, and division.

3. The division of the cell cytoplasm is called .

4. During which stage of the cell cycle is DNA copied?

5. Do all cells take the same amount of time to divide? Explain.

6. How does the surface area-to-volume ratio limit cell size?

5.1 VocabularyCheck


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Name ______________________________ Class ___________________ Date __________________

© Houghton Mifflin Harcourt Publishing Company Holt McDougal Biology 1 Cell Growth and Division


CELL REPRODUCTION

Cell Division Read the passage below, which covers topics from your textbook. Answer the questions that follow.

Mitosis is a continuous process that is divided into four phases: prophase, metaphase, anaphase, and telophase. Prophase is the first phase of mitosis. Prophase begins with the shortening and tight coiling of DNA into rod-shaped chromosomes that can be seen with a light microscope. During the S phase, each chromosome is copied. The two copies of each chromosome—called chromatids—stay connected to one another by the centromere. At this time, the nucleolus and the nuclear membrane break down and disappear. Two pairs of dark spots called centrosomes appear next to the disappearing nucleus. The centrosomes move toward opposite poles of the cell, and spindle fibers radiate from the centrosomes in preparation for mitosis.

Metaphase is the second phase of mitosis. During metaphase, kinetochore fibers move the chromosomes to the center of the dividing cell.

During anaphase, the chromatids of each chromosome separate at the centromere and slowly move toward opposite poles of the dividing cell. After the chromatids separate, they are considered to be individual chromosomes.

Telophase is the fourth phase of mitosis. After the chromosomes reach opposite ends of the cell, the spindle fibers disassemble and the chromosomes return to a less tightly coiled chromatin state. A nuclear envelope forms around each set of chromosomes, and a nucleolus forms in each of the newly forming cells.

Match each statement with the phase of mitosis it describes. Write the letter corresponding to the correct phase in the space provided.

SKILL: Sequencing Information

In this exercise, matching the statement with the stage of mitosis will help you learn the sequence of events of mitosis.

a. prophase c. anaphase

b. metaphase d. telophase 1. ________ Chromatids of each chromosome separate at the centromere.

Name ______________________________ Class ___________________ Date __________________


2. ________ Copied DNA coils into chromosomes. 3. ________ Spindle fibers disassemble. 4. ________ Kinetochore fibers move chromosomes to the cell’s center. 5. ________ Centrosomes appear next to the disappearing nucleus. 6. ________ A nucleolus forms in each newly formed cell. 7. ________ Chromatids move toward opposite poles of the dividing cell. 8. ________ Spindle fibers radiate from the centrosomes. 9. ________ A nuclear envelope forms around each set of chromosomes.

Write your answers in the spaces provided.

SKILL: Interpreting Graphics

10. The figure below shows the phases of mitosis. Using the information contained in the passage, write the name of the structure on each lettered line. On the numbered lines below the figure, name the stage of mitosis corresponding to the number on the figure. Use the following labels: “Anaphase,” “Centromere,” “Centrosomes,” “Metaphase,” “Nuclear envelope,” “Prophase,” “Spindle fibers,” and “Telophase.”

Circle the letter of the word or phrase that best completes the analogy.

15. Prophase is to centrosomes as telophase is to a. chromatids. b. nucleolus. c. kinetochore fibers. d. spindle fibers.

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5.2Chromosomescondense*atthestartofmitosis.

DNA is a double-stranded molecule, like a twisted ladder. A chromosome is one long piece of DNA. Every one of your body cells has 46 chromo-somes. The DNA in each chromosome has many genes.

During interphase, when the cell is not dividing, the chromosomes are loose—kind of like 46 pieces of spaghetti. During mitosis, the DNA is condensed* and organized. This helps the chromosomes to stay untangled while the cell divides.

The figure below shows how the DNA strand turns into the very condensed form of a chromosome during mitosis.

Look at the picture of the condensed, duplicated chromosome. Recall that the chromosomes are copied during the S stage that happens before mitosis. This condensed, duplicated chromosome looks like an “X.” The right half of the X and the left half are copies of each other.

Dna double helix Each continuous, double-stranded DNA molecule makes one chromosome.

Dna andhistones DNA wraps around proteins called histones, forming chromatin.

ChromatinInteractions between parts of the histones further compact the DNA.

supercoiled Dna The chromatin coils more and more tightly around orga-nizing proteins.

Condensed, duplicated chromosomeThe condensed, duplicated chromosomes can be lined up and separated during mitosis.

centromere

chromatid

telomere

telomere

DnAcondensestightlyduringtheearlystagesofmitosis.

CHRoMosoMEsTRuCTuRE

histone

Mitosis and CytokinesisKEyConCEPT Cells divide during mitosis and cytokinesis.


condense to make something smaller or more compact


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They are identical. Each half of a duplicated chromosome is called a chromatid (KROH-muh-tihd). Together, the two identical chromatids are called sister chromatids. The sister chromatids are held together at a place called the centromere (SEHN-truh-meer).

explain how a chromatid and a duplicated chromosome are related.

Mitosisandcytokinesisproducetwogeneticallyidenticaldaughtercells.

By the end of interphase, a cell is ready to divide. Mitosis divides the DNA, and cytoki-nesis divides the rest of the cell. The result is two identi-cal cells. Mitosis happens in all of your body cells—except cells that form eggs or sperm. Your cells divide for growth, development, and repair. Single-celled organisms use cell division to reproduce.

Mitosis and cytokinesis are continuous processes. They do not happen in steps. However, scientists have divided the processes into steps to make them easier to understand and discuss. The four main phases of mitosis are prophase, metaphase, anaphase and telophase. Cytokinesis begins at the end of anaphase or in telophase. These steps are shown in the figure to the right.

What is one reason your body cells need to divide?

1

these fibers help the cell divide.

inTERPHAsE

Parent cell

Mitosis divides a cell’s nucleus into two nuclei, each with an identical set of Dna.

MiTosis

Prophase Chromatin condenses into tightly coiled duplicated chromosomes. the nuclear membrane breaks down.

Metaphase the chro-mosomes line up in the middle of the cell.

2

Anaphase sister chroma-tids separate to opposite sides of the cell.

3Telophase nuclear membranes start to form again. Chromo-somes begin to uncoil.

CyToKinEsis

Cytokinesis divides cytoplasm between two daughter cells, each with a genetically identical nucleus. the cells enter inter-phase and begin the cycle again.

nucleus with Dna

4



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chromosome centromerehistone prophase

chromatin metaphase

telomere anaphasechromatid telophase

1. Label the diagram below with the terms chromosome, chromatid, centromere, and telomere.

2. Draw and label each phase of mitosis—prophase, metaphase, ana-phase, and telophase—in the circles below:

3. On the diagram above, in question 2, circle the part of the process in which cytokinesis occurs.

4. The word part telo- means “end.” How does this word part relate to the meaning of the terms telomere and telophase?

1. During which stage of the cell cycle is DNA copied?

2. How many chromatids are there in one duplicated chromosome?

3. Two identical daughter cells result from mitosis and cytokinesis. In what ways are they “identical”?

5.2 VocabularyCheck


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5.2 TheBigPicture



Name ______________________________ Class ___________________ Date __________________



REGULATION OF THE CELL CYCLE

Gene Expression in Development and Cell Division

Read the passage below, which covers topics from your textbook. Answer the questions that follow.

A tumor is an abnormal proliferation of cells that results from uncontrolled, abnormal cell division. The cells of a benign tumor remain within a mass. Examples of benign tumors are the fibroid cysts that occur in a woman’s breasts or uterus. Most benign tumors can be removed by surgery.

In a malignant tumor, the uncontrolled dividing cells may invade and destroy healthy tissues elsewhere in the body. Malignant tumors are more commonly known as cancer. Metastasis is the spread of cancer cells beyond their original site. When metastasis occurs, the cancer cells break away from the malignant tumor and travel to other parts of the body, where they invade healthy tissue and begin forming new tumors. Malignant tumors can be categorized according to the types of tissues they affect. Carcinomas grow in the skin and the tissues that line the organs of the body. Sarcomas grow in bone and muscle tissue. Lymphomas are solid tumors that grow in tissues that form blood cells.

Read each question and write your answer in the space provided.

SKILL: Forming Analogies

In an analogy, one must analyze the relationship between two words and then identify another pair of words that have the same relationship. In the analogy “Glove is to hand as sock is to foot,” the relationship is article of clothing to part of the body where worn.

1. Complete the following analogy: “Skin is to carcinoma as bone is to ______ .” 2. What relationship was used to form the analogy in question 1?

__________________________________________________________________

Circle the letter of the word or phrase that best completes the analogy. 3. Sarcomas are to muscle tissue as lymphomas are to

a. uterus. c. tissues that form blood cells. b. lungs. d. Both (a) and (b)

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SEcTIoN

8.2DnAiscomposedoffourtypesofnucleotides.

Since the 1920s scientists have known the chemical parts of the DNA molecule. DNA is a very long polymer, or chain of repeating units. The units, or monomers, that make up DNA are called nucleotides (NOO-klee-oh-tydz). Each nucleotide has three parts: a phosphate group, a base, and a sugar.

There are four different types of DNA nucleotides: cyto-sine (C), thymine (T), adenine (A), and guanine (G). All of the nucleotides contain a phosphate group and a deoxyribose sugar. They differ in their nitrogen-containing bases, as shown in the table below.

Notice that thymine (T) and cytosine (C) have nitrogen-containing bases with a single-ring structure. Adenine (A) and guanine (G) are bases with a double-ring structure. A single molecule of human DNA is made of billions of nucleotides.

THEfoURniTRoGEn-ConTAininGBASESofDnA

PyRimiDinES=SinGLERinG PURinES=DoUBLERinG

NameofBase Structuralformula Model NameofBase Structuralformula Model

N

NH2

NH

C

C

C

HN

HC N

C O

C A

G

T

C

N

NH2

NH

C C C

C C

C

C

C

CH CH N N N N

HN HN

HN

NH NH

NH NH

HC HC

HC

N N

N

NH2 NH2

C C

C C

NH NH C C

HC HC

HC HC

HC HC

C C C CH3

O O

C C O O

O O

N N

NH2 NH2

C O

N

NH2

NH

C

C

C

HN

HC N

C O

C A

G

T

C

N

NH2

NH

C C C

C C

C

C

C

CH CH N N N N

HN HN

HN

NH NH

NH NH

HC HC

HC

N N

N

NH2 NH2

C C

C C

NH NH C C

HC HC

HC HC

HC HC

C C C CH3

O O

C C O O

O O

N N

NH2 NH2

C O

N

NH2

NH

C

C

C

HN

HC N

C O

C A

G

T

C

N

NH2

NH

C C C

C C

C

C

C

CH CH N N N N

HN HN

HN

NH NH

NH NH

HC HC

HC

N N

N

NH2 NH2

C C

C C

NH NH C C

HC HC

HC HC

HC HC

C C C CH3

O O

C C O O

O O

N N

NH2 NH2

C O

N

NH2

NH

C

C

C

HN

HC N

C O

C A

G

T

C

N

NH2

NH

C C C

C C

C

C

C

CH CH N N N N

HN HN

HN

NH NH

NH NH

HC HC

HC

N N

N

NH2 NH2

C C

C C

NH NH C C

HC HC

HC HC

HC HC

C C C CH3

O O

C C O O

O O

N N

NH2 NH2

C O

N

NH2

NH

C

C

C

HN

HC N

C O

C A

G

T

C

N

NH2

NH

C C C

C C

C

C

C

CH CH N N N N

HN HN

HN

NH NH

NH NH

HC HC

HC

N N

N

NH2 NH2

C C

C C

NH NH C C

HC HC

HC HC

HC HC

C C C CH3

O O

C C O O

O O

N N

NH2 NH2

C O

N

NH2

NH

C

C

C

HN

HC N

C O

C A

G

T

C

N

NH2

NH

C C C

C C

C

C

C

CH CH N N N N

HN HN

HN

NH NH

NH NH

HC HC

HC

N N

N

NH2 NH2

C C

C C

NH NH C C

HC HC

HC HC

HC HC

C C C CH3

O O

C C O O

O O

N N

NH2 NH2

C O

N

NH2

NH

C

C

C

HN

HC N

C O

C A

G

T

C

N

NH2

NH

C C C

C C

C

C

C

CH CH N N N N

HN HN

HN

NH NH

NH NH

HC HC

HC

N N

N

NH2 NH2

C C

C C

NH NH C C

HC HC

HC HC

HC HC

C C C CH3

O O

C C O O

O O

N N

NH2 NH2

C O

N

NH2

NH

C

C

C

HN

HC N

C O

C A

G

T

C

N

NH2

NH

C C C

C C

C

C

C

CH CH N N N N

HN HN

HN

NH NH

NH NH

HC HC

HC

N N

N

NH2 NH2

C C

C C

NH NH C C

HC HC

HC HC

HC HC

C C C CH3

O O

C C O O

O O

N N

NH2 NH2

C O

thymine

cytosine

adenine

guanine

circle the names of the four nucleotides shown in the table above.

Structure of DNAKEyConCEPT DNA structure is the same in all organisms.

The small units, or monomers, that make up a strand of DNA are called nucleotides.Nucleotides have three parts.

VISUALVOCAB

nitrogen-containingbase

phosphategroup

deoxyribose(sugar)

• phosphate group: one phosphorus with four oxygens

• deoxyribose: ring-shaped sugar• nitrogen-containing base: a single

or double ring built around nitrogen atoms and carbon atoms

Interactive Reader 129

3F, 6A, 6B


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* AcADemic VocAbUlARy

accurate correct

WatsonandCrickdevelopedanaccurate*modelofDnA’sthree-dimensionalstructure.

For a long time, scientists hypothesized that DNA in all organisms was made up of equal amounts of the four nucleotides. Then Erwin Chargaff found that the proportion of the bases differs from organism to organ-ism. In the DNA of each organism, the amount of A equals the amount of T, and the amount of C equals the amount of G.

Then in the early 1950s, the scientists Rosalind Franklin and Maurice Wilkins used x-rays to make a kind of photograph of DNA molecules. These photographs did not show what DNA looks like, but they showed patterns that gave clues about DNA’s structure.

Around the same time, the scientists James Watson and Francis Crick were working together to figure out DNA struc-ture, too. Based on the work of other scientists, they hypoth-esized that DNA might have a spiral, or helix (HEE-lihks), shape. Watson and Crick saw Franklin’s photos and used the information to complete their model of DNA structure.

In April 1953 Watson and Crick published their DNA model in a paper in the journal Nature. They found that nucleotides fit together in a double helix. Two strands of DNA wrap around each other like a twisted ladder.

What new information did Watson and crick contrib-ute to science?

nucleotidesalwayspairinthesameway.Each side of the DNA double helix is a long strand of phosphates and sugars, connected by covalent bonds. The two sides of the double helix are held to each other by hydrogen bonds that form between the bases in the middle. Each individual hydrogen bond is weak, but together they are strong enough to hold the shape of DNA. The bases of the two DNA strands always bond according to the base pairing rules: T pairs with A, and C pairs with G.

The bases pair in this way because of hydrogen bonds. Notice that A and T form two hydrogen bonds, whereas C and G form three.

To help remember the rules of base pairing, notice that the letters G and C have a similar shape. Once you know that G and C pair together, you know that A and T also pair together. If the sequence of bases on one DNA strand is CTGA, the other DNA strand will be GACT.

Watson and Crick’s model showed DNA in the shape of a double helix.



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DG

GC

T

T

A

A

G

T

T

A

A

G

G

G

T

T

A

A

G C

C

C

C

G C

C

C

D

D

D

D

DD

D

D

D

DD

D

DD

D

D

D

DD

DD

P

PP

P P

P

P

PP

P

P

P

P

P

P

P P

P

P

P

P

P

P

P

P

P

P

P

D

D

D

D

D

D

D

D

D

BASEPAiRinGRULES

ThebasepairingrulesdescribehownucleotidesformpairsinDnA.TalwayspairswithA,andGalwayspairswithC.

A

G

T

C

T

C

A

G

hydrogenbond covalentbond

G c

AT

Gc

T A

The nitrogen-con-taining bases bond in the middle to form the rungs of the DNA ladder.

This ribbonlike part represents the phos-phategroups and deoxyribosesugar mol-ecules that make up DNA’s “backbone.”

What sequence of bases would pair with GTAcG?

nucleotide base pairing rules

double helix

1. Label the drawing at the right with the terms nucleotide, base pairing rules, and double helix. Write each term and draw a line that connects the term to the appropriate part of the drawing.

2. What are the three different parts of a nucleotide?

3. What are the names of the four nucleotides?

4. Use the base pairing rules to write the sequence that would pair with the following sequence: TCACGTA

8.2 vocabularyCheck


Mark It Up

8.2 TheBigPicture



Name ______________________________ Class ___________________ Date __________________


Holt McDougal Biology 1 From DNA to Proteins

Section 2: Structure of DNA

Study Guide A KEY CONCEPT DNA structure is the same in all organisms.

VOCABULARY

MAIN IDEA: DNA is composed of four types of nucleotides.

1. In the space below, draw a nucleotide and label the phosphate group, the nitrogen-containing base, and the deoxyribose sugar.

Fill in the blank with the word or phrase that best completes the sentence.

2. How many types of nucleotides are present in DNA? ___________

3. All nucleotides have two parts that are the same: the deoxyribose sugar and __________________. The third part, _____________________, is different.

MAIN IDEA: Watson and Crick developed an accurate model of DNA’s three-dimensional structure. Circle the word or phrase that best completes the statement.

4. Franklin’s data revealed that the structure of DNA is uniform / variable in width.

5. Watson and Crick determined the three-dimensional shape of DNA by building models / building genomes.

6. DNA base pairing results in a molecule that has a uniform width. A sugar-phosphate backbone is on the inside / outside. Inside the structure, a base with two rings always pairs with a base with one / two ring(s).

nucleotide double helix base pairing rules

Name ______________________________ Class ___________________ Date __________________


Holt McDougal Biology 2 From DNA to Proteins


MAIN IDEA: Nucleotides always pair in the same way.

7. The T nucleotide pairs with the ___________ nucleotide, and the C nucleotide pairs with the ___________ nucleotide.

8. In the space below, draw a DNA double helix. Label the sugar-phosphate backbone, the nitrogen-containing bases, and the hydrogen bonds.

Vocabulary Check Fill in the blank with the word or phrase that best completes the sentence.

9. The DNA double helix is similar to a spiral staircase: the ___________________________ is like the twisting handrails of the staircase, and the ______________________________ are like the steps that connect the railings to each other.

Select from the lettered list to fill in the blanks in the sentence below.

10. The base pairing rules of DNA relate to Chargaff’s rules. The base pairing rules state that A only pairs with T and C only pairs with G. Therefore, the amount of A will be _______________ the amount of T, and the amount of C will be ______________ the amount of G. a. less than b. more than c. equal to



Week 3: June 15-17

7 DNA Mutations

6E -8.7 Mutations Interactive Reader Pgs. 146-148 -Section 7 Study Guide B Pgs. 1-2

8

Genetics

6F

-6.4 Traits, Genes, & Alleles Interactive Reader Pgs. 102-103 -6.5 Traits & Probability Interactive Readers Pgs. 104-107 -Active Reading: Fundamentals of Genetics Pgs. 3-4

Last Day /Check Out: June 17

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8.7Somemutationsaffectasinglegene,whileothersaffectanentirechromosome.

In biology a mutation means a change in an organism’s DNA. A muta-tion can happen during replication and affect a single gene. A mutation can also happen during meiosis and affect a whole chromosome.

GenemutationsThere are different types of gene mutations.

• A point mutation is when an incorrect nucleotide is put into a DNA molecule during replication. If the error is not fixed by DNA polymerase, the DNA is perma-nently changed. For example, the figure to the right shows a CTC codon that is changed to a CTA codon. As a result, the wrong amino acid is added—aspartic acid instead of glutamic acid.

• A frameshift mutation is the addition or removal of a nucleotide in the DNA sequence. This results in a change in the reading frame. Recall the importance of the reading frame from Section 8.5. Think back to the sentence “THE CAT ATE THE RAT.” If the letter E is removed, or deleted, from the first “THE,” the reading frame is shifted. The result is “THC ATA TET HER AT…” The reading frame is also shifted if a nucleotide is added, or inserted.

ChromosomalmutationsErrors in meiosis can result in changes in large parts of a chromosome. Recall that crossing over is a normal process in which chromosomes exchange pieces. Errors in crossing over or in other parts of meiosis can result in chromosomes with two copies of the same gene. Pieces of non-homologous chromosomes might even be exchanged.

What is the difference between a gene mutation and a chromosomal mutation?

MutationsKEyConCEPT mutations are changes in DNA that may or may not affect phenotype.

TyPESofmUTATionS

Amutationisachangeinanorganism’sDnA.

Normal Point mutation

Frameshift mutation (insertion) Frameshift mutation (deletion)

Leu Glu Ser Asp

Leu GluLeu

added base

deletedbase

Leu Ser Asp

Glu

mutatedbase

Asp

Ser IleVal Arg

UUU

CC C

C C C

TTT GG

G GG

G AAA

A A A

UUU

CC C

C C

TTT

GG GG

G G A AAA

A A A UUUU

CC C

C C C

T

T

TT T GG

G GG

G AAA

A A A A

UUUU

CC

C C C

TTT GG

G G

G A

A

AAA

A A A

DNA

mRNA

protein

DNA

mRNA

protein

DNA

mRNA

protein

DNA

mRNA

protein

Normal Point mutation

Frameshift mutation (insertion) Frameshift mutation (deletion)

Leu Glu Ser Asp

Leu GluLeu

added base

deletedbase

Leu Ser Asp

Glu

mutatedbase

Asp

Ser IleVal Arg

UUU

CC C

C C C

TTT GG

G GG

G AAA

A A A

UUU

CC C

C C

TTT

GG GG

G G A AAA

A A A UUUU

CC C

C C C

T

T

TT T GG

G GG

G AAA

A A A A

UUUU

CC

C C C

TTT GG

G G

G A

A

AAA

A A A

DNA

mRNA

protein

DNA

mRNA

protein

DNA

mRNA

protein

DNA

mRNA

protein


6E


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mutationsmayormaynotaffectphenotype.Whether a mutation affects an organism depends on many different things.

• Typeofmutation A point mutation only affects one codon. A frameshift mutation usually has a bigger effect because it changes the whole reading frame and can affect many codons.

• Impactontheaminoacidsequence A change in one codon can still have a big effect. For example, if a codon for an amino acid is changed into a stop codon, transcription would end at the wrong place. A point mutation may also have no effect. Recall that more than one codon can code for the same amino acid. For example, CGU, CGC, CGA, and CGG all code for arginine. A point muta-tion that changes the last nucleotide of this codon would have no effect on the resulting amino acid.

• Impactontheresultingprotein Some changes might not affect the resulting protein’s shape or function. Other changes might prevent the protein from functioning. For example, a mutation could change the active site of an enzyme and prevent the enzyme from binding to its substrate.

• Typeofcell Recall that mutations that occur in germ cells can be passed on to offspring. Mutations in body cells cannot be passed on to offspring.

Give one example of a mutation that would not affect an organism’s phenotype.

mutationscanbecausedbyseveralfactors.Mutations happen. But cells have tools to repair them. For example, DNA polymerase has a “proofreading” function to fix errors. However, mutations can happen faster than the body’s repair system can work. Some mutations are the result of errors that happen normally in the cell. Other mutations are caused by things in the environment.

• Replicationerrors DNA polymerase proofreads replication, but a small number of errors are not fixed. Over time, there are more and more errors. Eventually these mutations affect how the cell works. There is evidence that a build-up of mutations is a major cause of aging.

This point mutation changed a codon for cysteine into a stop codon.

U CG

U G A

U CG

U G A

cysteine

stop



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• Mutagens Some conditions and substances in the environment can cause DNA mutations—such as UV light and some chemicals. Things in the environment that can change DNA are called mutagens.

If mutations cause changes that affect the control over cell division, cancer may result.

What are two examples of mutagens?

mutation frameshift mutation

point mutation mutagen

1. What is the difference between a mutation and a mutagen?

2. What is the difference between a point mutation and a frameshift mutation?

3. Is a mutation that happens during meiosis likely to affect a single gene or an entire chromosome? Explain.

4. Give an example of one mutation that will affect an organism’s pheno-type and one mutation that will not affect phenotype.

8.7 vocabularyCheck


Mark It Up

8.7 TheBigPicture



Name ______________________________ Class___________________Date__________________


Holt McDougal Biology 1 From DNA to Proteins Study Guide B Section 7: Mutations

Section 7: Mutations

Study Guide B KEY CONCEPT Mutations are changes in DNA that may or may not affect phenotype.

VOCABULARY

MAIN IDEA: Some mutations affect a single gene, while others affect an entire chromosome.

1. List two types of gene mutations.

_______________________________________________________________ 2. List two types of chromosomal mutations.

_______________________________________________________________ 3. Which type of mutation affects more genes, a gene mutation or a chromosomal

mutation?

_______________________________________________________________ 4. What leads to gene duplication?

_______________________________________________________________ 5. What is a translocation?

_______________________________________________________________

Below is a string of nucleotides. (1) Use brackets to indicate the reading frame of the nucleotide sequence. (2) Copy the nucleotide sequence into the first box and make a point mutation. Circle the mutation. (3) Copy the nucleotide sequence into the second box and make a frameshift mutation. Use brackets to indicate how the reading frame would be altered by the mutation.

mutation frameshift mutation point mutation mutagen

A G G C G T C C A T G A

6.

7.

Name ______________________________ Class___________________Date__________________


Holt McDougal Biology 2 From DNA to Proteins Study Guide B Section 7: Mutations

result in coding regions 9.

10. may occur

in

Point mutations 11.

resultin 8. 12.

no change

nonfunctional protein

Study Guide B continued

MAIN IDEA: Mutations may or may not affect phenotype. Fill in the cause-and-effect diagram below to explain how a point mutation may or may not affect phenotype.

13. For a mutation to be passed to offspring, in what type of cell must it occur?

_______________________________________________________________

MAIN IDEA: Mutations can be caused by several factors.

14. Can DNA polymerase catch and correct every replication error?

_______________________________________________________________ 15. What is a mutagen?

_______________________________________________________________ 16. How does UV light damage the DNA strand?

_______________________________________________________________

_______________________________________________________________

Vocabulary Check 17. What is a mutation?

_______________________________________________________________ 18. If a nucleotide is deleted from a strand of DNA, what type of mutation has

occurred?

_______________________________________________________________

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Traits, Genes, and AllelesKEyConCEPT Genes encode proteins that produce a diverse range of traits.

Thesamegenecanhavemanyversions.As you learned, the units of inheritance that Mendel studied are now called genes. You can think of a gene as a piece of DNA that stores instructions to make a certain protein. Each gene is located at a particular place on a chromosome called a locus. Just like a house has an address on a street, a gene has a locus on a chromosome.

Many things come in different forms. For example, bread can be wheat, white, or rye. Most genes have many forms, too. An allele (uh-LEEL) is any of the different forms of a gene. The gene for pea shape, for example, has two alleles—one for round peas and another for wrinkled peas.

Your cells, like the pea plant’s cells, have two alleles for each gene—one on each chromosome of a homologous pair. The term homozygous (hoh-moh-ZY-guhs) means the two alleles of a gene are the same—for example, both alleles are for round peas. The term heterozygous (heht-uhr-uh-ZY-guhs) means the two alleles are different—for example, one allele is for wrinkled peas and one is for round peas.

Draw a circle around each of the alleles shown in the Visual Vocab to the right.

genesinfluencethedevelopmentoftraits.

For Mendel’s peas, if a plant was heterozygous for pea shape, the pea shape would be round. This is because the allele for round peas is dominant, or expressed when two different alleles are present. A recessive allele is expressed only when there are two copies of the recessive allele. A dominant allele is not better or stronger or more common; it is simply the allele that is expressed when there are two different alleles. Mendel studied traits that had just two alleles, one that was dominant and one that was recessive. Most traits involve much more complicated patterns of inheritance.

Alleles are represented with letters—capital letters for dominant alleles and lowercase letters for recessive alleles. For example, the dominant allele for round pea shape can be

seCTion

6.4

Homozygousalleles are identical to each other.

VISUAL VOCAB

Heterozygousalleles are different from each other.

homozygous alleles

heterozygous alleles

wrinkled

wrinkled round

wrinkled

The drawing on p. 93 shows a homolo-gous pair of duplicated chromosomes. Notice that here the chromosomes are drawn unduplicated. These are two homologous pairs of unduplicated chromosomes.

A dominantallele is expressed when two different alleles are present.

A recessiveallele is expressed only when two copies are present.

VISUAL VOCAB

genotype phenotype

wrinkled rounddominantrecessive

genotype phenotype

recessive recessivewrinkled wrinkled

R

r


6A, 6F


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written as R, for round. The recessive allele, for wrinkled pea shape, can be represented with the same letter, but lowercase—r.

A genotype is the set of alleles an organism has for a trait. For exam-ple, a genotype could be homozygous dominant (RR), heterozygous (Rr), or homozygous recessive (rr). A phenotype is what the resulting trait looks like—for example, round or wrinkled. A genome is all of an organism’s genetic material—all of the genes on all of the chromosomes.

What is the difference between a genotype and a phenotype?

gene recessive

allele genotype

homozygous phenotype

heterozygous genome

dominant

1. What is the difference between a gene and an allele?

2. What is the difference between a dominant allele and a recessive allele?

3. Fill in the blanks in the chart below regarding pea shape.

gEnoTyPE PHEnoTyPE HoMozygousoRHETERozygous

RR homozygous dominant

Rr round peas

rr homozygous recessive

4. Which of the alleles in the chart above is dominant?

6.4 VocabularyCheck


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6.4 TheBigPicture



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seCTion

6.5Punnettsquaresillustrategeneticcrosses.

A Punnett square is a grid* system for predicting all possible genotypes resulting from a cross. The outside edges, or axes*, of the grid represent the possible genotypes of gametes from each parent. The grid boxes show the possible genotypes of offspring from those two parents.

Let’s briefly review what you’ve learned about meiosis and segregation to examine how the Punnett square works. Both parents have two alleles for each gene. These alleles are repre-sented on the axes of the Punnett square. During meiosis, the chromosomes—and therefore the alleles—are separated. Each gamete can receive only one of the alleles, but not both. When fertilization happens, gametes from each parent join together and form a diploid cell with two copies of each chromosome. The new cell has two alleles for each gene. This is why each box shows two alleles. One is from each parent.

What do the letters on the axes of the Punnett square represent?

Amonohybridcrossinvolvesonetrait.Thus far, we have studied crosses of one trait. Monohybrid crosses are crosses that examine the inheritance of only one specific trait—for example, flower color. If we know the genotypes of the parents, we can use a Punnett square to predict the genotypes of the offspring.

The Punnett squares on the next page show the results of three different crosses:

• Homozygous dominant crossed with homozygous recessive (FF ff )• Heterozygous crossed with heterozygous (Ff Ff )• Heterozygous crossed with homozygous recessive (Ff ff )

Traits and ProbabilityKEyConCEPT The inheritance of traits follows the rules of probability.

* ACADEMIC VOCAbulARY

grid a layout of squares, like on graph paper

axes lines that act as points of reference

The Punnettsquareis a grid system for predicting possible genotypes of offspring.

VISUAL VOCAB

A a

A AA Aa

Aa aaa

Parent1alleles

Pare

nt2

al

lele

s possible genotypes of offspring


3F, 6F, 6G


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MonoHyBRiDCRossEs

F F

homozygous dominant parent (FF)

homozygous recessive parent (ff) f

Ff Ff

Ff Ff f

F f

heterozygous parent (Ff)

heterozygousparent (Ff)

F

FF Ff

Ff ff f

f f

homozygous recessive parent (ff)


F

Ff Ff

ff ff f

All offspring receive a dominant allele, F, from one parent and a recessive allele, f, from the other parent. So all offspring—100 percent—have the heterozygous genotype Ff. And 100 percent of offspring have purple flowers.

From each parent, half of the offspring receive a dominant al-lele, F, and half receive a recessive allele, f. Therefore, one-fourth of the offspring have an FF genotype, one-half are Ff, and one-fourth are ff. In other words, the genotypic ratio is 1:2:1 of FF : Ff : ff. Remember that both FF and Ff genotypes have a purple phenotype. The phenotypic ratio is 3 :1 of purple:white flowers.

All of the offspring receive a recessive allele, f, from the homo-zygous recessive parent. Half receive a dominant allele, F, from the heterozygous parent, and half receive the recessive allele, f. The resulting genotypic ratio is 1:1 of Ff:ff. The phenotypic ratio is 1:1 of purple:white.

Suppose that we had a purple-flowered pea plant but did not know its genotype. It could be FF or Ff. We could figure out its genotype by cross-ing the purple-flowered plant with a white-flowered plant. We know that the white-flowered plant is ff, because it has the recessive phenotype. If the purple-flowered plant is FF, the offspring will all be purple. If the purple-flowered plant is Ff, half of the offspring will have purple flowers, and half will have white flowers. Crossing a homozygous recessive organism with an organism of unknown genotype is called a testcross.

What are the genotypes of offspring from an FF ff cross?

F f


heterozygousparent (Ff)

F

FF Ff

Ff ff f

f f

homozygous recessive parent (ff)


F

Ff Ff

ff ff f



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Adihybridcrossinvolvestwotraits.So far, we have examined monohybrid crosses, or crosses that examine only one trait. Mendel also performed dihybrid crosses, or crosses that examine the inheritance of two different traits.

For example, Mendel crossed a purebred plant that had yellow round peas with a purebred plant that had green wrinkled peas. He wanted to see if the two traits—pea shape and color—were inherited together. The first generation of offspring all looked the same, and they were all heterozygous for both traits. The second generation of offspring is shown in the figure to the right. In addition to green wrin-kled and yellow round peas, there were also green round and yellow wrinkled peas. In other words, Mendel found that pea shape and color were independent of each other—they were not inherited together. Mendel’s second law of genetics is the law of independent assortment, which states that alleles of different genes separate indepen-dently of one another during gamete formation, or meiosis. Different traits are inherited separately.

What is the difference between a monohybrid cross and a dihybrid cross?

Hereditypatternscanbecalculatedwithprobability.

Probability is the likelihood, or chance, that a particular event will happen. It predicts the average number of times something happens, not the exact number of times.

Probability =number of ways a specific event can occur

number of total possible outcomesSuppose you flip a coin. There is a 1 _ 2 chance it will land on heads, and a 1 _ 2 chance that it will land on tails. Suppose you flip two coins. For each one, the chance it will land on heads is 1 _ 2 . But for both to land on heads, the chance is 1 _ 2 1 _ 2 1 _ 4 .

DiHyBRiDCRoss

This dihybrid cross is heterozygous-heterozygous.

YR

YR

F1 generation

F2 generation

Yr

yR

yr

Yr yR yrYyRr

YyRr

yyrr

yyRryyRR

yyRr

YYRR YYRr YyRR YyRr

YYRr YYrr YyRr Yyrr

YyRR YyRr

YyRr Yyrr

Mono- means “one,” and di- means “two.” A mono-hybrid cross looks at one trait and a dihybrid cross looks at two traits.

VoCABulARy



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These probabilities can be applied to meiosis, too. Suppose a germ cell has heterozygous alleles for a trait, for example, Ff. A gamete has a 1 _ 2 chance of getting an F and a 1 _ 2 chance of getting an f. If two heterozygous plants are crossed, what is the chance that the offspring will be FF? There is a 1 _ 2 chance that the sperm will carry an F and a 1 _ 2 chance that the egg will carry an F. Therefore, there is a 1 _ 2 1 _ 2 1 _ 4 chance that the offspring will be FF. Probability can be used to determine all of the possible genotypic outcomes of a cross.

If you flip two coins, what is the prob-ability that they will both land on tails?

Punnett square dihybrid cross

monohybrid cross law of independent assortment

testcross probability

Choose the correct term from the list for each description.

1. crossing an organism of unknown genotype with a homozygous reces-sive organism

2. a cross to examine one trait only

3. a cross to examine two different traits

4. Fill in the Punnett square and list the genotype and phenotype ratios.

6.5 VocabularyCheck


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6.5 TheBigPicture

PRoBABiliTyAnDHEREDiTy

The coins are equally likely to land heads up or tails up.

H

H T

T

HH Two sides of coin 1

Two sides of coin 2

1 4 HT 1

4

HT 1 4 TT 1

4

1 2

1 2

1 2

1 2

Genotype ratio:

Phenotype ratio:

F f

f Ff

f



Name ______________________________ Class ___________________ Date __________________

© Houghton Mifflin Harcourt Publishing Company Holt McDougal Biology 3 Meiosis and Mendel


FUNDAMENTALS OF GENETICS

Genetic Crosses Read the passage below, which covers topics from your textbook. Answer the questions that follow.

Biologists use a diagram called a Punnett square to aid them in predicting the probable distribution of inherited traits in the offspring.

In rabbits, the allele for black coat color (B) is dominant over the allele for brown coat color (b). The Punnett square below shows the predicted results of crossing two rabbits that are both heterozygous (Bb) for coat color. As you can see, 1/4 (25 percent) of the offspring are predicted to have the genotype BB, 1/2 (50 percent) are predicted to have the genotype Bb, and 1/4 (25 per-cent) are predicted to have the genotype bb. Thus, 3/4 (75 percent) of the offspring resulting from this cross are predicted to have a black coat. One-fourth (25 percent) of the offspring are predicted to have a brown coat. The ratio of the genotypes that appear in offspring is called the genotypic ratio. The ratio of the offspring’s phenotypes is called the phenotypic ratio.

Read each question and write your answer in the space provided. SKILL: Interpreting Graphics 1. The figure below is a Punnett square. Using the

information provided in the passage and the figure, answer the questions that follow.

Name ______________________________ Class ___________________ Date __________________

© Houghton Mifflin Harcourt Publishing Company Holt McDougal Biology 4 Meiosis and Mendel

a. What is the purpose of this figure?

_______________________________________________________________ b. The passage states that both parents are heterozygous for coat color. What

does this statement mean?

_______________________________________________________________

_______________________________________________________________ c. How can you use the information in the figure to determine the coat color of

the parents?

_______________________________________________________________

_______________________________________________________________ d. What are the genotypes of predicted homozygous offspring?

_______________________________________________________________

_______________________________________________________________ e. What is the probable genotypic ratio of the cross represented in the graphic?

_______________________________________________________________ f. What is the probable phenotypic ratio of the cross represented in the

graphic?

_______________________________________________________________

Read the question and write your answer in the space provided.

SKILL: Vocabulary Development 2. The prefix pheno- is derived from a Greek term meaning “to show.” How does

knowledge of this word part aid in decoding the term phenotype?

_________________________________________________________________

_________________________________________________________________

_________________________________________________________________

Circle the letter of the word or phrase that best completes the statement.

3. Another Punnett square yielded 2 black: 2 brown. This is an example of a a. genotypic ratio. b. probability equation. c. percentage. d. phenotypic ratio.

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