Biology Chapter 14

Interest Grabber A Family Tree

|  NOTEBOOK #1

|  To understand how traits are passed on from generation to generation, a pedigree, or a diagram that shows the relationships within a family, is used. In a pedigree, a circle represents a female, and a square represents a male. A filled-in circle or square shows that the individual has the trait being studied. The horizontal line that connects a circle and a square represents a marriage. The vertical line(s) and brackets below that line show the child(ren) of that couple.

Interest Grabber cont. | 1. This pedigree shows the inheritance of

attached ear lobes. Which parent has attached ear lobes?

| 2. How many children do the parents have? Which child has attached ear lobes?

| 3. Which child is married? Does this child’s spouse have attached ear lobes? Do any of this child’s children have attached ear lobes?

Autosomal Disorders

caused by

include include include

Autosomol Disorders

Recessive alleles

Dominant alleles

Codominant alleles

Albinism Galactosemia Tay-Sachs disease

Huntington’s disease

Sickle cell disease

Cystic fibrosis

Phenylketonuria Achondroplasia Hypercholes- terolemia

Pedigree

A circle represents a female.

A square represents a male.

A horizontal line connecting a male and female represents a marriage.

A vertical line and a bracket connect the parents to their children. A half-shaded

circle or square indicates that a person is a carrier of the trait. A completely

shaded circle or square indicates that a person expresses the trait.

A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait.

Pedigree of Queen Victoria

Blood Groups

Phenotype (Blood Type) Genotype

Antigen on Red Blood Cell

Safe Transfusions To From

ABO Blood Type Multiple Alleles

|  Type A: AA, AO

|  Type B: BB, BO

|  Type AB: AB

|  Type O: OO

Blood Type Frequency

NOTEBOOK #2

1. What is a pedigree? 2. In a pedigree, females are

represented by what? Males? 3. In a pedigree, how is a carrier

represented? 4. What are the four blood types? 5. List the blood types in order from

most common to least common.

Interest Grabber- Notebook#3

Gender Benders |  You may remember that in humans,

the sperm cells may carry an X chromosome or a Y chromosome, while egg cells have only X chromosomes. Sometimes, errors during meiosis in one of the parents produce offspring with an abnormal number of sex chromosomes.

Interest Grabber cont. |  1. On a sheet of paper, construct a Punnett

square for the following cross: XX x XY. Fill in the Punnett square. What does the Punnett square represent? According to the Punnett square, what percentage of the offspring from this genetic cross will be males? What percentage will be females?

|  2. On a sheet of paper, construct a Punnett square for the following cross: XXX x XY. Fill in the Punnett square. How is this Punnett square different from the first one you constructed? What might have caused this difference?

|  3. How do the offspring in the two Punnett squares differ?

Interest Grabber

X

X X

X

X X X

Y

Y

Nondisjunction

Homologous chromosomes fail to separate

Meiosis I: Nondisjunction

Meiosis II

Nondisjunction (Trisomy)

|  Nondisjunction- failure of chromosomes to separate during cell division. Results in extra chromosomes in body cells.

Down’s Syndrome (Nondisjunction) Karyotype

Solving Sex-linked Problems

|  The gene for hemophilia is found on the X chromosome

|  Sex-linked traits are also called X-linked traits

|  Hemophilia is a blood disease that does not allow the blood to clot

Colorblindness (sex-linked)- gene for the disease is carried on the X chromosome

Father (normal vision)

Colorblind Normal vision

Mother (carrier)

Daughter (normal vision)

Son (normal vision)

Daughter (carrier)

Son (colorblind)

Male

Female

Red-Green Colorblindness |  Sex-linked

disease caused by the recessive gene

|  Female |  Normal: XCXC

|  Carrier: XCXc

|  Red-Green: XcXc

|  Male |  Normal: XCY

|  Red-Green: XcY http://colorvisiontesting.com/ishihara.htm

Crossing Over | Crossing Over-

part of a chromatid on one homolog may break and rejoin with one of the chromatids belonging to the second homolog

Notebook #4

1. What is nondisjunction? What does it cause?

2. What is a sex-linked trait? Give an example.

3. How are sex-linked traits passed on?

4. Explain crossing over.

Duplication A duplication occurs when part of a chromosome is copied (duplicated) abnormally, resulting in extra genetic material from the duplicated segment

Translocation Translocation is a chromosomal disorder in which a fragment of a CHROMOSOME breaks from its original chromosome and attaches itself to a different chromosome.

Deletion A deletion occurs when a chromosome breaks and some genetic material is lost.

Insertion In this example, one nucleotide (adenine) is added in the DNA code, changing the amino acid sequence that follows

Inversion Inversions occur when a chromosome breaks in two places and the resulting piece of DNA is reversed and re-inserted into the chromosome.

Notebook #5

1. What is duplication? 2. What is translocation? 3. What is a deletion? 4. What is an insertion? 5. What is an inversion?

Interest Grabber – Notebook #6

Analyzing Inheritance |  Offspring resemble their parents. Offspring

inherit genes for characteristics from their parents. To learn about inheritance, scientists have experimented with breeding various plants and animals.

|  In each experiment shown in the table on the next slide, two pea plants with different characteristics were bred. Then, the offspring produced were bred to produce a second generation of offspring. Consider the data and answer the questions that follow.

Interest Grabber

|  1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?

|  2. How do the characteristics of the second generation compare to the characteristics of the first generation?

Parents

Long stems × short stems

Red flowers × white flowers

Green pods × yellow pods

Round seeds × wrinkled seeds

Yellow seeds × green seeds

First Generation

All long

All red

All green

All round

All yellow

Second Generation

787 long: 277 short

705 red: 224 white

428 green: 152 yellow

5474 round: 1850 wrinkled

6022 yellow: 2001 green

Gregor Mendel | Austrian Monk who

studied the genetics of pea plants

| His work was not recognized until 1900, several years after his death

|  Because of his work he is known as the Father of Genetics

Mendel’s Experiment

Principles of Dominance P Generation F1 Generation F2 Generation

Tall Short Tall Tall Tall Tall Tall Short

Genetic Terms |  Dominant- prevents the expression of the recessive

genes {  Represented by capital letters T

|  Recessive- masked by the dominant trait {  Represented by a lower case letter t

|  Homozygous- two genes that are the same: TT, tt

|  Heterozygous- two genes that are different: Tt

|  Genotype- actual genes of an organism: TT, Tt, tt

|  Phenotype- physical appearance of an organism: Tall, Short

|  Probability- the likelihood that an event will occur: 50:50 chance of getting heads or tails

Mendel’s Seven F1 Crosses

on Pea Plants Seed

Shape Flower Position

Seed Coat Color

Seed Color

Pod Color

Plant Height

Pod Shape

Round

Wrinkled

Round

Yellow

Green

Gray

White

Smooth

Constricted

Green

Yellow

Axial

Terminal

Tall

Short

Yellow Gray Smooth Green Axial Tall

Punnett Square Complete Dominance

| Genotype: |  4Gg

| Phenotype: |  4 green

Tt X Tt Cross

Genotype: 1 TT : 2Tt : 1tt Phenotype: 3 Tall : 1 short

Punnett Squares – Notebook #7

Create Punnett Squares with the following crosses. Be sure to give the Genotypic and Phenotypic ratios. 1.  SEED SHAPE: HOMOZYGOUS ROUND X HETEROZYGOUS ROUND 2.  POD COLOR: HETEROZYGOUS GREEN X HOMOZYGOUS YELLOW 3.  FLOWER COLOR: HETEROZYGOUS PURPLE X HETEROZYGOUS PURPLE 4.  SEED COLOR: HOMOZYGOUS YELLOW X HOMOZYGOUS YELLOW

Notebook #8

1. Who is Gregor Mendel? 2. What is the difference between the

P, F1, and F2 generations? 3. What is the difference between

dominant and recessive? 4. What is the difference between

homozygous and heterozygous? 5. What is the difference between

genotype and phenotype?

Interest Grabber Height in Humans

| Height in pea plants is controlled by one of two alleles; the allele for a tall plant is the dominant allele, while the allele for a short plant is the recessive one. What about people? Are the factors that determine height more complicated in humans?

Interest Grabber cont. | 1. Make a list of 10 adults whom you

know. Next to the name of each adult, write his or her approximate height in feet and inches.

| 2. What can you observe about the heights of the ten people?

| 3. Do you think height in humans is controlled by 2 alleles, as it is in pea plants? Explain your answer.

Interest Grabber – Notebook #9

Tossing Coins |  If you toss a coin, what is the probability

of getting heads? Tails? If you toss a coin 10 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.

1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected?

2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected?

3. If you compiled the results for the whole class, what results would you expect?

4. How do the expected results differ from the observed results?

Interest Grabber continued

Concept Map

concluded that

which is called the

which is called the

Gregor Mendel

Law of Dominance

Law of Segregation

Pea plants

“Factors” determine traits

Some alleles are dominant, and some alleles are recessive

Alleles are separated during gamete formation

experimented with

Independent Assortment in Peas

The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes. Independent assortment helps account for the many genetic variations observed in plants, animals and other organisms.

Incomplete Dominance in Four O’Clock Flowers

Genotype: 4 RW Phenotype: 4 Pink

Incomplete dominance occurs when one allele is not completely dominant over another. They both contribute to the phenotype equally.

Codominance Blood type is a codominant trait, meaning that each allele fully expresses itself. In other words, neither allele dominates the other and each allele is equally emphasized.

RR = red cow hairs RW = red and white cow hairs WW = white cow hairs

BB = black feathers BW = black and white feathers WW = white feathers

Notebook #10 1. What is the principle of independent

assortment and when does it occur?

2. What is incomplete dominance?

3. What is codominance?

4. Compare and contrast incomplete dominance and codominance.