Question 1

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

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Question 2

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.

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Question 3

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 4

When X-rays penetrate cells,electrons are ejected from atoms of molecules.Stable molecules can be transformed into which two types of hazardous materials?

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Question 5

How were insertion sequences (IS elements)first discovered?

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Question 6

In a survey of 240,000 human births,six achondroplastic births were recorded to parents who were unaffected.Given that this form of dwarfism is caused by a fully penetrant,dominant,autosomal gene,what is the mutation rate?

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Question 7

Which human condition is caused by unrepaired UV-induced lesions?

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Question 8

Describe the action of the enzyme transposase.

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Question 9

What is meant by the term photoreactivation repair?

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Question 10

The process of error correction of mismatched bases carried out by DNA polymerases is called ________.

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Question 11

Under certain conditions,the rate of mutation of a particular gene may be determined in humans.Name three properties of the mutation that would favor the most direct determination of mutation rate in humans.

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Question 12

Apurinic sites (AP sites)involve a spontaneous loss of a(n)________ in an intact double-helix DNA molecule.

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Question 13

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,whereas others do not.

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Question 14

It has been found that a particular "+ —" combination of frameshift mutations in gene X gives a wild-type phenotype,whereas a "— +" combination gives a mutant phenotype,even though the sites of insertion/deletion are the same.How might these results be explained?

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Question 15

What is the common influence of ultraviolet light on DNA?

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Question 16

Recent discoveries on causes of fragile-X syndrome,myotonic dystrophy,and Huntington disease indicate which type of genetic alteration?

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Question 17

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

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Question 18

A mutation that occurs naturally,without exposure to a known mutagen,is called a ________.

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Question 19

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

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Question 20

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

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Quiz 14: Gene Mutation,DNA Repair,and Transposition