Chapter 13: Altering the Genetic Material: Mutation, DNA Repair, and Cancer

Question 1

Define mutation.

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Answer 1

a heritable change in the genetic material

Question 2

T or F: New mutations are much more likely to be harmful than beneficial to the individual.

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Answer 2

true

Question 2

What are the two basic types of change that gene mutations can cause?

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Answer 2

1) the base sequence within a gene can be changed
2) one or more base pairs can be added to or removed from a gene

Question 3

What type of mutation is this?

A wild-type DNA sequence is 5’ -ACACGTTGAT- 3’.
It is converted to 5’ -ACACGTTAAT - 3’.

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Answer 3

point mutation/base substitution; where G is replaced with A

Question 4

Where must a mutation occur if its is to directly affect an amino acid sequence?

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Answer 4

the coding region of a protein-encoding gene

Question 5

There are 4 different types of effects that point mutations have on polypeptides. Name each one and briefly describe them.

BONUS: DRAW IT!

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Answer 5

1. Silent (causes no change)
2. Missense (changes one amino acid in the polypeptide)
3. Nonsense (changes a normal codon to a stop codon and shortens the polypeptide)
4. Frameshift (produces a different amino acid sequence)

Question 6

A point mutation affects only a single ____ pair within the DNA.

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Answer 6

base

Question 7

____ and ________ mutations can cause more dramatic changes to a polypeptide sequence than ________ mutations.

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Answer 7

nonsense and frameshift; missense

Question 8

T or F: Mutations within noncoding sequences can affect gene expression.

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Answer 8

true

Question 9

What effects do the following sequences have on mutation?
Promoter, transcriptionl regulatory element, splice sites, translational regulatory element, and intergenic region.

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Answer 9

Promoter: increase or decrease the rate of transcription
Transcriptional RE: alter the regulation of transcription
Splice sites: alter ability of pre-mRNA to be properly spliced
Translational RE: alter the ability of mRNA to be translationally regulated
Intergenic region: not as likely to affect gene expression

Question 10

Define a germ-line mutation.

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Answer 10

a mutation that occurs in a germ-line cell, which gives rise to gametes; can be passed from parent to offspring

Question 11

Consider a germ-line mutation that occurs in a sperm which fertilizes a normal egg to produce a zygote. In the individual that results from this zygote ____% of the cells will contain the mutation, and ____ % of the gametes produced by that individual will carry the mutation.

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Answer 11

100; 50

Question 12

T or F: A somatic mutation is transmitted to the offspring of the individual that carries it.

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Answer 12

false; it is NOT

germ-line mutations ARE passed from parent to offspring

Question 13

T or F: Germ-line mutations affect the whole organism, while somatic mutations affect a limited area of the body.

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Answer 13

true

Question 14

Bacterial colonies can be transferred from a master plate to secondary plates in the same configuration using a transferring agent such as a sterile velevet cloth. What is this technique know as?

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Answer 14

replica plating

Question 15

Which two scientists are responsible for using replica plating to show that mutations are random events?

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Answer 15

Joshua and Esther Lederberg

Question 16

The results of the replica plating experiment performed by the Lederbergs supported their hypothesis that mutations are random events by demonstrating what?

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Answer 16

The T1 mutation developed in the original population before exposure to bateriophages.

Question 17

What type of mutation results from abnormalities that naturally occur during biological processes?

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Answer 17

spontaneous mutations

Question 18

Define induced mutations.

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Answer 18

Mutations that are caused by environmental agents that enter the cell and alter the structure of DNA.

Question 19

The technique of replica plating allows for the:

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Answer 19

identification of transformed cells

Question 20

How do the effects of germ-line mutations in a parent progress over the lifetime of an offspring receiving that mutation?

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Answer 20

All of the cells of the individual’s body, but only half of the gametes produced by that individual will carry the mutation.

Question 21

What are two types of physical mutagens?

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Answer 21

X-rays and UV light

Question 22

What are the three outcomes that are caused by chemical mutagens?

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Answer 22

1) covalent modification (ex: nitrous acid deaminates bases)
2) base analogues (ex: 5-Bromouracil and 2-Aminopurine)
3) distortion of the DNA double helix (ex: benzo[a]pyrene

Question 23

Define ioning and nonionizing radiation.

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Answer 23

Ioning: Radiation that is short-wavelength and high energy, and often leads to base deletions and breaks in one or both DNA strands
Nonionizing: Radiation that has a longer wavelength and lower energy, which penetrates the skin and often leads to thymine dimers

Question 24

What are thymine dimers?

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Answer 24

In DNA, a type of pyrimidine dimer that can cause a mutation; a site where two adjacent thymine bases become covalently crosslinked to each other

Question 25

Which test was developed in the 1970s, to evaluate the ability of a substance to cause muations?

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Answer 25

the Ames test

Question 26

Who was the Ames test developed by?

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Answer 26

Bruce Ames

Question 27

T or F: UV lights are ionizing, whereas X-ray and gamma rays are forms of nonionizing radiation.

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Answer 27

false; the opposite

Question 28

T or F: All living things possess mechanisms allowing them to minimize mutation.

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Answer 28

true

Question 29

Exposure to chemical mutagens can lead to mutations because chemical mutagens can cause:

Hint: 2 answers

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Answer 29

insertions and deletions during DNA replication
and
inappropriate base pairing during DNA replication

Question 30

What is NER? Does it occur in prokaryotes? What about eukaryotes?

Answer 30

NER stands for nucleotide excision repair, and it is the most common DNA repair system found in all eukaryotes and prokaryotes

Question 31

A compound is subjected to the Ames test to evaluate its ability to cause mutation. If the subsance is a mutagen, what results are expected?

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Answer 31

there will be more bacterial colonies on the plate exposed to the mutagen than on the control plate

Question 32

Identify the function of each protein that is involved in nucelotide excision repair in E.Coli. (UvrC, UvrD, DNA polymerase, DNA ligase, UvrA/UvrB complex)

BONUS: DRAW IT! :)

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Answer 32

UvrC: cuts DNA on both sides of the damaged site
UvrD: removes the damaged region
DNA polymerase: synthesizes new DNA to fill in the gap
DNA ligase: seals newly synthesized DNA to the original strand
UvrA/UvrB complex: identifies a damaged site

Question 33

Compare base analogs to DNA bases.

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Answer 33

base analog structure is similar to DNA bases but don’t pair correctly and cause errors in DNA replication
(ex: 5-Bromouracil and 2-Aminopurine)

Question 34

What is the purpose of the Ames test?

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Answer 34

it’s an experimental procedure that tests whether substances cause a mutation (make histidine); uses salmonella typhimurium that cannot synthesize histidine

Question 35

Can mutagens cause mutations by altering the genetic code of an organism?

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Answer 35

No; mutagens can cause mutations by chemically alterting the DNA molecule and distrupting the replication of DNA.