Biology 9

Unit 8:Cell Communication/Genetics

Created by: Jeff Wolf and Mike Graff

Objectives: After completing this Learning Quest the student will…

Describe and label the parts to a DNA and RNA molecule.

Explain how genetic information flows from DNA to RNA to Proteins.

Explain the concept of the Genetic Code.

Give examples of mutations.

Directions1. Follow the instructions in

the Anticipation Guide found in this PowerPoint Presentation.

2. Follow the instructions and answer all questions found in the Learning Guide.

3. Follow the instructions in the Conclusion Guide.

4. ALL THREE GUIDES CAN BE FOUND IN THIS LEARNING POWERPOINT QUEST.

Anticipation Guide (Page 1)• The following slides will be a

quick review of material covered in Unit 3: Nutrition and Biological Molecules.

• The structure of a DNA molecule can be broken down into three specific parts. The first part, the nucleotide (a) consists of three parts: a sugar, a phosphate, and a nitrogenous base. In these simplified diagrams, the three parts of a nucleotide are symbolized with shapes and colors.

Anticipation Guide (Page 2)• The second part of the

DNA molecule is the DNA strand (b) is composed of nucleotides linked into a backbone, with attached pieces consisting of the 4 bases. A strand has a particular sequence of four bases abbreviated A, G, C, and T.

Anticipation Guide (Page 3)• The third part of the DNA

molecule is the Double helix (c ). A double helix consists of two DNA strands bonded together by strand bases. These bonds are hydrogen bonds and are therefore individually weak. However these bonds zip the two strands together with a strength to give the double helix stability.

Anticipation Guide (page 4)• When doctors talk about children

inheriting certain traits such as blue eyes, red hair, or some genetic disorder from their parents, the genetic material that these children received from their parents is DNA.

• The directions for these traits are actually chemically coded in a “nucleic acid.” This chemical code needs to be translated from DNA into proteins.The cell’s use a chemical in your body called RNA to take charge of this process.

Anticipation Guide (Page 5)• The chemical code used by DNA consists of

four chemical bases.• The four chemicals and their abbreviations are

found below.– Adenine (A).– Guanine (G).– Thymine (T).– Cytosine (C ).

• Genes can be passed along to offspring because inheritance is based upon the DNA code. In the core of this double helix are the bases mentioned above that bond together to create this DNA molecule. In this code A can pair only with T, and G can only pair with C. To find out more about

the DNA molecule, moveto the next slide.

Learning Guide (Page 1)• DNA gets its name

because of deoxyribose, the sugar found within the DNA nucleotide (a) .

• The full name for DNA is deoxyribonucleic acid. “Nucleic” refers to the DNA’s exact location within the nucleus of the cell.

• Refer to pages 176 – 190 of you textbook.

Learning Guide (Page 2) • There are three

differences between DNA and RNA:

1. The RNA sugar is a ribose rather than a deoxyribose.

2. The nitrogenous base Thymine is replaced by the base Uracil.

3. DNA is a double helix, whereas, RNA is a single stranded structure.

Learning Guide (Page 3)• Once biologists were sure that DNA was

the genetic material, understanding how DNA contributed to a persons inheritance was the next big discovery.

• This discovery was made by American James D. Watson and Englishman Francis Crick.. These two scientists were the first to develop a wire model of the DNA structure.

• Watson and Crick determined that DNA was not only a spiral helix but that the diameter of the helix was always the same. The thickness of the DNA helix suggested that it was made up of two polynucleotide strands and therefore was a double helix.

Learning Guide (Page 4)• The diagrams below show two ways scientists illustrate the DNA

molecule. Diagram (a) shows the sugar-phosphate backbones as blue ribbons and the complementary bases are shown in shades of green and orange. Diagram (b) is the detailed structure of the DNA molecule.

Learning Guide (Page 5)• When cells divide or

organisms reproduce, genetic instructions need to be passed on from one generation to the next. To accomplish this replication process, the parent DNA molecule will unwind and act as a template to build a new DNA molecule that will be an exact copy of the original parent molecule. (see the diagram to the right for a further explanation).

Learning Guide (Page 6)• The new daughter DNA

molecules are formed by using ½ of the parent DNA molecules to match nitrogen bases. Therefore, Cytosine (C) from the parent’s DNA molecule will connect with Guanine (G) from the new daughter’s part of the DNA molecule to create a new double helix DNA molecule . This process is called replication.

Learning Guide (Page 7)

• In the process of transcription, genetic information is transferred from DNA to an RNA molecule.

• In the translation stage, genetic information from the RNA molecule is read and a protein molecule is assembled from these instructions.

• Transcription and translation will be discussed in more detail starting on page 10 of the Learning Guide.

Learning Guide (Page 8)• The genetic information

that needs to be decoded is referred to as codons. These codons are groups of three nitrogen bases located on the messenger RNA.

• These codons identify the correct amino acid that needs be put into place as the protein are assembled.

Learning Guide (Page 9)• In order to identify the

correct amino acid, the codon must first be looked up on a table of mRNA codons. Note the table to the left.

• For example, if the codon UUU is displayed, the amino acid phenylalanine (Phe) would be called for.

• Notice there are 64 different codon messages and 20 common amino acids displayed to the left.

Learning Guide (Page 10)• As mentioned before transcription is the stage in which genetic

information transfers from the DNA molecule to an RNA molecule. This genetic information is then able to be used within the cell for the creation of proteins. It is these proteins that will then determine how that organism or tissue will look and work.

Learning Guide (Page 11)

• Notice that the table also contains one start message/codon and three stop messages/codons. These messages are important because it signifies, much like punctuation in a sentence where the protein production process should begin and where it should end.

Learning Guide (Page 12)• To transfer the information

from mRNA to make a protein, a process called translation must occur. It begins with the codon being read and a helper called transfer RNA assisting in this stage.tRNA is referred to as the anticodon. Transfer RNA pairs up with the correct 3 base code on mRNA. As a result transfer RNA attaches the correct amino acid called for onto the growing protein chain.

Learning Guide (Page 13)• The six step diagram below demonstrates the entire process of creating

new genetic material from DNA to RNA and eventually to protein.

Learning Guide (Page 14)• When a child is born with a medical condition such as sickle cell

anemia, the disease can be traced back through a difference in one protein.

• This change in a nucleotide sequence of DNA is called a mutation. • Mutations can involve a large region (diagram A) of a chromosome or

just a single nucleotide pair (diagram B).

Diagram ADiagram B

Learning Guide (Page 15)

• Mutations can occur in a number of ways. Mutations can result from errors in DNA replication or recombination errors are called spontaneous mutations.

• When the source of mutation come from physical or chemical agents these sources are called mutagens. The most common mutagen is high energy radiation. Others include sunlight and cigarette smoke.

• These mutagens may lead to cancer. Refer to page 214 – 215.

Learning Guide (Page 16)• Most mutagens are cancer causing agents

called carcinogens. These carcinogens bring about changes in DNA.

• Potent carcinogens created by X-ray or radiation can cause leukemia and brain cancer. Carcinogens created by ultraviolet (UV) radiation can cause skin cancer and a deadly type of skin cancer called melanoma.

• The substance known to cause more types of cancer than any other single agent is tobacco. Smoking causes the mutation of cells and promotes rapid cell division and therefore the development of tumors.

Learning Guide (Page 17)

• Please print the following pages and then read and summarize the article below.

http://www.lalc.k12.ca.us/uclasp/ISSUES/landfills/case_love.html

Conclusion Guide (Page 1)• See your teacher with your article review and then move on to the next

assignment. You may need to return to your notes, the PowerPoint Learning Quest, or use the textbook to complete this assignment.

Conclusion Guide (Page 2)• Use the words provided in the list to best

complete the following statements (see next slide). Use these choices:

mRNA

nitrogen bases

frameshift mutation

point mutation

tRNA

translation

codon

double helix

chromosomal mutation

replication

nondisjunction

cancer

Conclusion Guide (Page 3)

1. During the process of transcription, DNA serves as the template for making ______, which leaves the nucleus and travels to the ribosomes.

2. A _________ involves the addition or deletion of a single base in a DNA molecule.

3. Watson and Crick developed the _________ model of DNA.4. Thymine, adenine, guanine, and cytosine are _________________.

mRNA

nitrogen bases

frameshift mutation

point mutation

tRNA

translation

codon

double helix

chromosomal mutation

replication

nondisjunction

cancer

Conclusion Guide (Page 4)

5. The process by which DNA makes a coy of itself is called _______.6. Each set of three nitrogen bases representing an amino acid is

referred to as a _________.7. _________ brings amino acids to the ribosomes for assembly of

proteins.8. A change in a single base pair of DNA molecule is called a ______.

mRNA

nitrogen bases

frameshift mutation

point mutation

tRNA

translation

codon

double helix

chromosomal mutation

replication

nondisjunction

cancer

Conclusion Guide (Page 5)

9. ________ is the failure of a par of homologous chromosomes to separate properly during meiosis.

10. The process of converting RNA code into an amino acid sequence is called _____________.

11. When parts of chromosomes are broken off and lost or reattached incorrectly during mitosis or meiosis , the result is a _________.

12. Mutations in DNA can result in cells reproducing rapidly, producing the disease called ___________________.

mRNA

nitrogen bases

frameshift mutation

point mutation

tRNA

translation

codon

double helix

chromosomal mutation

replication

nondisjunction

cancer

Works Cited

• http://www.sicmm.org/pictures/dna.png• http://www.accelrys.com/support/life/image

s/dna.jpg• http://www.ebi.ac.uk/microarray/biology_in

tro_files/WatsonCrick.jpe

• http://www.acmecompany.com/stock_thumbnails/12440.love_canal_locator.gif

After completing the test, move onto Unit #9.