Module 7 Molecular Genetics

3.7.4 page 3

Read

Causes of Mutations

 

Some mutations are spontaneous and occur naturally in the cell. One cause of this type of mutation is incorrect base pairing by DNA polymerase during DNA replication.

 

Factors in our environment can also cause mutations; these mutations are referred to as induced mutations. There are two categories of mutagens that cause these induced mutations: physical and chemical. You have likely been exposed to the physical mutagen, x-rays, if you have ever broken a bone. Learn more about physical and chemical mutagens by reading pages 644 and 645 of your textbook. As you read, create a list to organize the chemical and physical mutagens you discover. In your list, describe how they cause mutations and what the outcome of the mutation can be (ie. Cancer). Search the Internet and view the video below to help you add to this list. Place this list in your course folder for future reference when studying.

 

Watch and Listen

Watch the following video titled Genes, Mutations and Viruses: Alterations in the Genetic Code as it is an excellent review of this lesson. It shows animations of mutations, discusses causes of mutations, and even specifically mentions Sickle-cell anemia.

 

Reflect and Connect

Self-Check

Use the following information to answer the next two questions.

The following matches the normal coding sequence, with the codons in the top row and the resulting amino acids in the bottom row.
mRNA codons:	–GUU	– CAU	– UUG	– ACU	– CCC	– GAA	– GAA
amino acids	–val	– his	– leu	– thr	– pro	– glu	– glu

1. Identify the type of mutation that would occur if the first codon was changed as shown below: GUU is changed to GUC
   
   
   1. frameshift mutation: this would cause the entire reading frame of a protein to be altered
   2. nonsense mutation: this would render the protein unable to code for a functional gene
   3. silent mutation: this would have no effect on the cell’s metabolism
   4. mis-sense mutation: this would result in an altered DNA molecule
2. Identify the type of mutation that would occur if the third codon was changed as shown: UUG is changed to UAGG
   
   
   1. frameshift mutation: this would cause the entire reading frame of the gene to be altered
   2. nonsense mutation: this would render the gene unable to code for a functional polypeptide
   3. silent mutation: this would have no effect on the cell’s metabolism
   4. mis-sense mutation: this would result in an altered protein
3. What type of point mutations occurred when the third codon was changed from UUG to UAGG in the question above?
   
   
   1. substitution
   2. insertion
   3. deletion
4. Identify the type of mutation that would occur if the second codon was changed from CAU to CAA
   
   
   1. frameshift mutation: this would cause the entire reading frame of the gene to be altered
   2. nonsense mutation: this would render the gene unable to code for a functional polypeptide
   3. silent mutation: this would have no effect on the cell’s metabolism
   4. mis-sense mutation: this would result in an altered protein
5. What type of point mutation occurs when the second codon was changed from CAU to CAA in the question above?
   
   
   1. substitution
   2. insertion
   3. deletion
6. For a substance to be classified as a mutagen, it must cause
   
   
   1. a change in DNA.
   2. enzymes to denature.
   3. protein production
   4. mRNA to be produced
7. Distinguish between induced mutations and spontaneous mutations.
8. Distinguish between chemical mutagen and physical mutagen, then give an example of each.

Discussion

Look through some of your classmates’ mutagen summaries. Were any mutagens more commonly summarized? Where any mutagens unfamiliar to you? Choose one summary by another student/group and read it in detail. After having read this summary, think of two questions that you would like answered. Send these questions to the student/group to answer.

 

Module 7: Lesson 4 Assignment

There is no assignment for this lesson.