Ch 13 Altering the genetic material mutation, DNA repair and Cancer

Question 1

A mutation is best defined as:

Answer 1

a heritable change in the genetic material

Question 2

Mutations are essential for the long-term continuity of life because the supply the __________ that is the foundation for evolutionary change.

Answer 2

genetic variation

Question 3

Which of the following are ways that point mutations may alter a gene?

Answer 3

A base pair is removed from a gene.
A nucleotide is added to a gene.
The base sequence within the gene is changed.

Question 4

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

Answer 4

The coding region of a structural gene

Question 5

A heritable change in genetic material is known as a(n)

Answer 5

mutation

Question 6

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

Answer 6

True

Question 7

Place the following types of mutations in order from the least effect on polypeptide sequence at the top to the most dramatic effect on polypeptide sequence at the bottom.

Answer 7

silent
missense
nonsense

Question 8

How do point mutations affect DNA sequences?

Answer 8

by adding or subtracting a single base pair

by substituting one base for another

Question 9

Consider the following wild-type DNA sequence: 5’-CCAAGGTT-3’. Which of the following mutations is a base substitution?

Answer 9

5’-CCCAGGTT-3’

Question 10

Mutations in noncoding sequences:

Answer 10

may affect gene expression

Question 11

A mutation may affect the amino acid sequence of a polypeptide only if it occurs within the

Answer 11

coding sequence of a structural gene.

Question 12

Mutations outside a gene’s coding sequence can affect gene expression. Which of the following sites, when mutated, would affect transcription?

Answer 12

Promoter

Operator site

Question 13

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

Answer 13

100% and 50%

Question 14

True or false: Nonsense and frameshift mutations generally result in less dramatic changes to a polypeptide sequence than missense mutations.

Answer 14

False

Question 15

Somatic mutations are not transmitted to an individual’s offspring because:

Answer 15

they do not occur in the gametes

Question 16

Mutations that occur in noncoding sequences may affect ___

Answer 16

gene expression

Question 17

Bacterial colonies can be transferred from a master plate to secondary plates in the same configuration using a transferring agent such as a sterile velvet cloth. This technique is known a

Answer 17

replica plating

Question 18

A spontaneous point mutation may be caused during DNA replication when the enzyme ___ ____
puts the wrong base in a newly-synthesized strand.

Answer 18

DNA polymerase

Question 19

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

Answer 19

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

Question 20

Induced mutations are caused by:

Answer 20

environmental agents

Question 21

How do somatic mutations affect an individual’s offspring?

Answer 21

The mutation does not occur in germ line cells and therefore does not affect the offspring

Question 22

The effects of ___________ mutagens on DNA structure is varied. Some can alkylate bases, others act as base analogues, and a few can insert between bases in the double helix and cause additions or deletions.

Answer 22

chemical

Question 23

Which of the following are ways that ionizing radiation can alter DNA structure?

Answer 23

• base deletion

- breaks in one or both DNA strands

Question 24

What is the process in which bacterial colonies are transferred from a master plate to secondary plates in the same configuration using a transferring agent such as a sterile velvet cloth?

Answer 24

Replica plating

Question 25

What is a thymine dimer?

Answer 25

A site where two adjacent thymine bases become covalently cross-linked to each other

Question 26

____ are small segments of DNA that can insert at various sites in the genome. If they insert into a gene, they may cause a spontaneous mutation.

Answer 26

Transposons

Question 27

Mutations can be divided into two main types. Spontaneous mutations result from abnormalities in biological processes while _____ mutations are caused by environmental agents that enter the cell and alter the structure of the DNA

Answer 27

induced

Question 28

Nitrous acid, nitrogen mustard, 5-bromouracil, and benzo(a)pyrene are examples of ______________ mutagens.

Answer 28

chemical

Question 29

Which of the following are ways that chemical mutagens covalently modify the structure of nucleotides?

Answer 29

Alkylation of bases

Deamination of bases

Question 30

X-rays and ultraviolet light are examples of ______ mutagens.

Answer 30

physical

Question 31

Nonionizing radiation, such as ultraviolet light, can lead to:

Answer 31

the formation of a thymine dimer

Question 32

The ____________ test, which was developed in the 1970s, is used to evaluate the ability of a substance to cause mutations.

Answer 32

Ames

Question 33

A ______________ ______________ is a site where two adjacent thymine bases become covalently cross-linked to one another.

Answer 33

thymine and dimer

Question 34

Which of the following are chemical mutagens?

Answer 34

Nitrous acid
Benzopyrene
Ethyl methanesulfonate
Nitrogen mustard

Question 35

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

Answer 35

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

Question 36

Which of the following are physical mutagens?

Answer 36

X-rays

UV light

Question 37

Which of the following organisms have the ability to repair DNA and thus minimize mutations?

Answer 37

all living things

Question 38

What is the purpose of the Ames test?

Answer 38

Evaluation of the ability of a substance to cause mutation

Question 39

Organisms possess different types of DNA repair systems. In a type called ____ repair, an enzyme recognizes and removes an alkyl group, thus restoring the base to its original structure.

Answer 39

direct

Question 40

In nucleotide excision repair, what serves as the template for synthesis of new DNA to replace the damaged strand?

Answer 40

The complementary strand of DNA

Question 41

Which of the following exhibit nucleotide excision repair (NER)?

Answer 41

Plants
Humans
Mice
Bacteria

Question 42

In the Ames test, you expose S. typhimurium cells that cannot synthesize histidine to compound X, then plate them on a medium lacking histidine. The next day you observe a higher number of colonies on this plate versus the control plate, which has bacteria with no exposure. What reasonable conclusion can you draw?

Answer 42

Compound X is a mutagen

Question 43

Arrange the events that occur in nucleotide excision repair in E. coli in the correct order. Start with the earliest step on top.

Answer 43

• the UvrA-UvrB complex identifies a damaged site
• UvrC makes cuts on both sides of the damaged site
• UvrD binds and removed the damaged region
• DNA polymerase synthesizes new DNA to fill the gap
• DNA ligase seals the newly synthesized DNA to the original strand

Question 44

True or false: All living things possess mechanisms allowing them to minimize mutation.

Answer 44

True

Question 45

An alkylated base is recognized by an enzyme. The enzyme removes the alkyl group and restores the normal base structure. What type of DNA repair is this?

Answer 45

• A region of several nucleotides in the damaged strand is removed from the sequence
• The undamaged strand is used as a template to synthesize a normal strand

Question 46

Nucleotide excision repair (NER) is found in:

Answer 46

prokaryotes and eukaryotes

Question 47

Match each protein involved in nucleotide excision repair in E. coli with its function.

Answer 47

• cuts DNA on both sides of the damaged site
• removed the damaged region
• synthesizes new DNA to fill in the gap
• seals newly synthesized DNA to the original strand
• identifies a damaged site