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Exam 15: Gene Mutation,dna Repair,and Transposition

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Question 1

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Assuming one mutational event in a gene,on average,which of the following mutagens or mutational conditions would be expected to cause the most damage to a protein synthesized by such a mutagenized gene: 5-bromouracil,2-amino purine,ethylmethane sulfonate,or frameshift?

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Question 2

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Describe the mutagenic action of the following two mutagens: 5-bromouracil and ultraviolet light.

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The mutagen 5-bromouracil is a...

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Question 3

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Some mutagens cause genetic changes that can be "corrected" by reexposing cells to the same mutagen.Other mutagens do not behave in this way.Provide one example of each of these two types of agents and describe the mutational changes caused in DNA.Explain why some mutagens behave in one way,while others do not.

Loss-of-function mutations eliminate the function of a gene product and may be dominant or recessive.

Three human disorders-fragile X syndrome,myotonic dystrophy,and Huntington disease-are conceptually linked by a common mode of molecular upset.Describe the phenomena that link these disorders.

Some bacterial transposons,known as Tn elements,are larger than insertion sequences (IS elements) and contain protein-coding genes that have human health significance.What might such a bacterial transposon contain?

Describe the action of the enzyme transposase.

Ultraviolet light causes pyrimidine dimers to form in DNA.Some individuals are genetically incapable of repairing some dimers at "normal" rates.Such individuals are likely to suffer from ________.

Recombinational repair is activated when damaged DNA has escaped repair and the distortion disrupts the process of replication.Which gene is responsible recombinational repair?

Conditional mutations are more likely to result from a mutation caused by which of the following alterations to the coding region of a gene?

All insertion sequences (IS elements) contain two structural elements that are essential for their movement.What are these two elements?

DNA may be damaged from the by-products of normal cellular aerobic respiration.Name three of these electrophilic oxidants that are generally classified as reactive oxidants.

When treating an organism with a mutagen,although it is possible that homozygous mutations will occur,it is more likely that most new mutations will be heterozygous or hemizygous.

What is the Ames test,and how does it work?

One type of mutation involves the replacement of a purine with a purine,while another causes the replacement of a pyrimidine with a purine or the reverse.What general terms are associated with these two mutational phenomena?

A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be which of the following?

Considering the electromagnetic spectrum,identify likely mutagens from the following list: radio waves,microwaves,infrared,ultraviolet,X-rays,gamma rays,cosmic rays.

Postreplication repair is a system that responds after damaged DNA has escaped repair and failed to be completely replicated.

Mutations that arise in nature,from no particular artificial agent,are called ________.

Under which condition(s)might one have an amino acid substitution in a protein that does not result in an altered phenotype?