Ch. 18 Concept Check & Comprehension Questions Flashcards Preview

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Flashcards in Ch. 18 Concept Check & Comprehension Questions Deck (29):

A mutation that changes a codon into a stop codon is a ___ ___.

Nonsense mutation


A down promoter mutation causes the promoter of a gene to be ___ like the consensus sequence and ___ transcription.

Less, inhibits


A mutation in one gene that reverses the phenotypic effects of a mutation in a different gene is..

An intergenic suppressor


Which of the following is an example of a somatic mutation?

- a mutation in an embryonic muscle cell
- a mutation in an adult nerve cell


In the replica-plating experiments of the Lederbergs, bacterial colonies appeared at the same locations in each of two secondary plates because..

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


Which of the following is NOT an example of a spontaneous mutation?

A mutation caused by UV light


A point mutation is caused by ..

- depurination
- deamination
- tautomeric shift


One way that TNRE may occur involves the formation of ___ that disrupts ___.

A hairpin, DNA replication


Nitrous acid replaces amino groups with keto groups, a process called ___.

Deamination ?


A mutagen that is a base analog is..

5-bromouracil ?


In the Ames test, ___ number of colonies is observed if a substance ___ a mutagen, compared with the control that is not exposed to the suspected mutagen.

Significantly higher, is not ?


The function of photolyase is to repair..

Thymine dimers


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


In nucleotide excision repair in E. coli, the function of the UvrA/UvrB complex is to..

Detect DNA damage


Double-strand breaks can be repaired by..

- homologous recombination repair (HRR)
- nonhomologous end joining (NHEJ)


An advantage of translesion DNA polymerases is they can replicate ___, but a disadvantage is they ___.

Over damaged DNA, have low fidelity


Cause of position effects.

Explain what the term position effect means.

Position effect means that the expression of a gene has been altered due to a change in its position along a chromosome.


A position effect that alters eye color in Drosophilia.

Has the DNA sequence of the eye color gene been changed in part (b) compared with part (a)? How do we explain the phenotypic difference?

In part (b), the sequence of the eye color gene is not changed. The change in expression is due to a position effect.


Example of a somatic mutation.

Can this trait be passed to offspring?

A somatic mutation is not passed from parent to offspring.


Spontaneous depurination.

When DNA replication occurs over an apurinic site, what is the probability that a mutation will occur?

The probability is 75%.


Spontaneous deamination of cytosine and 5-methylcytosine.

Which of these two changes is more difficult for DNA repair enzymes to fix correctly? Explain why.

The deamination of methylcytosine is more difficult to repair because thymine is a normal base found in DNA. This makes it difficult for DNA repair enzymes to distinguish between the correct and altered strand.


Oxidation of guanine to 8-oxoguanine by a reactive oxygen species (ROS).

What is a reactive oxygen species?

A reactive oxygen species is a chemical that contains oxygen and may react with cellular molecules in a way that may cause harm.


Base pairing of 5-bromouracil and it's ability to cause mutation.

Does 5-bromouracil cause a transition or a transversion?

5-bromouracil causes a transition


Formation and structure of a thymine dimer.

In people, what is a common cause of thymine dimer formation and in what cell type(s) would it be most likely to occur?

Thymine dimer formation is often the result of exposure to UV light. It most commonly occurs in skin cells.


The Ames test for mutagenicity.

What is the purpose of the rat liver extract in this procedure?

Enzymes within the rat liver extract may convert non-mutagenic molecules into a mutagenic form. Adding the extract allows researchers to identify molecules that may be mutagenic in people.


Direct repair of damaged bases in DNA.

Which of these repair systems is particularly valuable to plants?

Photolyase is particularly valuable to plants, which are exposed to sun and susceptible to thymine dimer formation.


Nucleotide excision repair in E. coli.

Explain why cuts are made on both sides of the DNA damage.

Cuts are made on both sides of the DNA damage so the region can be removed by UvrD.


Mismatch repair in E. coli.

Which of these three proteins is responsible for ensuring that the mismatched base in the newly made daughter strand is the one that is removed?

MutH distinguishes between the parental strand and the newly made daughter strand, which ensures that the daughter strand is repaired.


DNA repair of a double-strand break via nonhomologous end joining.

What is an advantage and a disadvantage of this repair system?

An advantage of this DNA repair system is that it can occur at any stage of the cell cycle. A disadvantage is that it may be imprecise and result in a short deletion in the DNA.