Ch.19

A mutagen that is a base analog is ethyl methanesulfonate (EMS). 5-bromouracil. UV light. proflavin.

5-bromouracil.

Which of the following is not an example of a spontaneous mutation? A mutation caused by an error in DNA replication A mutation caused by a tautomeric shift A mutation caused by UV light All of the above are spontaneous mutations.

A mutation caused by UV light

Which of the following DNA repair systems may involve the removal of a segment of a DNA strand? Base excision repair Nucleotide excision repair Mismatch repair All of the above

All of the above

Which of the following mechanisms can result in gene conversion? DNA mismatch repair DNA gap repair Resolution of a Holliday junction Both a and b can result in gene conversion.

Both a and b can result in gene conversion.

Which of the following is an example of a somatic mutation? A mutation in an embryonic muscle cell A mutation in a sperm cell A mutation in an adult nerve cell Both a and c are examples of somatic mutations.

Both a and c are examples of somatic mutations.

One way that TNRE may occur involves the formation of _________ that disrupts ____________. a double-strand break, chromosome segregation an apurinic site, DNA replication a hairpin, DNA replication a free radical, DNA structure

a hairpin, DNA replication

During the molecular process of homologous recombination between homologous chromosomes, a Holliday junction forms. branch migration occurs. a heteroduplex region forms. all of the above occur.

all of the above occur.

A mutation in one gene that reverses the phenotypic effects of a mutation in a different gene is an intergenic suppressor. an intragenic suppressor. an up promoter mutation. a position effect.

an intergenic suppressor.

A point mutation could be caused by depurination. deamination. tautomeric shift. any of the above.

any of the above.

Nitrous acid replaces amino groups with keto groups, a process called alkylation. deamination. depurination. crosslinking.

deamination.

In nucleotide excision repair in E. coli, the function of the UvrA/UvrB complex is to detect DNA damage. make cuts on both sides of the damage. remove the damaged piece of DNA. replace the damaged DNA with undamaged DNA.

detect DNA damage.

Double-strand breaks can be repaired by homologous recombination repair (HRR). nonhomologous end joining (NHEJ). nucleotide excision repair (NER). either a or b.

either a or b.

A down promoter mutation causes the promoter of a gene to be _______ like the consensus sequence and _________ transcription. less, stimulates more, stimulates less, inhibits more, inhibits

less, inhibits

A mutation changes a codon that specifies tyrosine into a stop codon. This type of mutation is a missense mutation. nonsense mutation. frameshift mutation. neutral mutation.

nonsense mutation.

An advantage of translesion-replicating polymerases is that they can replicate _________________, but a disadvantage is that they _________________. very quickly, have low fidelity over damaged DNA, have low fidelity when resources are limited, are very slow over damaged DNA, are very slow

over damaged DNA, have low fidelity

In an Ames test, a ____________ number of colonies is observed if a substance ________ a mutagen, compared with the number of colonies for a control sample that is not exposed to the suspected mutagen. significantly higher, is significantly higher, is not significantly lower, is significantly lower, is not

significantly higher, is

Homologous recombination refers to the exchange of DNA segments that are similar or identical in their DNA sequences. in close proximity to one another. broken due to ionizing radiation. misaligned along a chromosome.

similar or identical in their DNA sequences.

A key difference between the original Holliday model and the double-strand break model is the way that the DNA strands are initially broken. branch migration occurs. a heteroduplex is formed. resolution occurs.

the DNA strands are initially broken.

In the replica-plating experiments of the Lederbergs, bacterial colonies appeared at the same locations on each of two secondary plates because T1 phage caused the mutations to happen. the mutations occurred on the master plate prior to T1 exposure and prior to replica plating. Both a and b are true. Neither a nor b is true.

the mutations occurred on the master plate prior to T1 exposure and prior to replica plating.

The function of photolyase is to repair double-strand breaks. apurinic sites. thymine dimers. all of the above.

thymine dimers.