Question 1

Which of the following best describes the initial step in homologous recombination repair of a double-strand break in DNA?

Accepted Answer

The 5' ends are digested to create 3' overhangs that invade the sister chromatid.

Question 2

A patient’s cells are unable to repair double-strand breaks during the G1 phase of the cell cycle. Which DNA repair pathway is most likely defective?

Accepted Answer

Nonhomologous end joining

Question 3

Which of the following is a potential consequence of nonhomologous end joining (NHEJ) repair of double-strand breaks?

Accepted Answer

Loss of several base pairs at the repair site

Question 4

Transposable elements can disrupt gene function in several ways. Which scenario below is most likely to result in a null mutation?

Accepted Answer

A transposable element inserts into a protein-coding exon.

Question 5

In the Ac-Ds system in maize, what is the role of the Ac (Activator) element?

Accepted Answer

It provides the transposase enzyme necessary for Ds movement.

Question 6

Which of the following best explains why some maize kernels are speckled in color?

Accepted Answer

The Ac element excises Ds from the C gene in some cells during development.

Question 7

Which of the following statements about retrotransposons is correct?

Accepted Answer

They use RNA as an intermediate and require reverse transcriptase for movement.

Question 8

A researcher finds a transposable element in Drosophila that is dispersed throughout the genome and is transcribed into large amounts of RNA. This element is most likely:

Accepted Answer

A copia element

Question 9

Hybrid dysgenesis in Drosophila is caused by which of the following genetic events?

Accepted Answer

High rates of P element transposition in the germ line

Question 10

Which of the following is a key difference between prokaryotic and eukaryotic gene regulation?

Accepted Answer

Eukaryotes have compartmentalized transcription and translation, allowing for more complex regulation.

Question 11

Which histone modification is generally associated with increased transcription?

Accepted Answer

Acetylation of histone tails

Question 12

What is the function of the SWI/SNF chromatin remodeling complex?

Accepted Answer

It repositions or removes nucleosomes to make DNA accessible for transcription.

Question 13

Which of the following is a cis-acting regulatory element that can increase the transcription of a gene from a distance?

Accepted Answer

Enhancer

Question 14

A mutation in the CAAT box of a gene’s promoter is most likely to affect:

Accepted Answer

The efficiency of basal transcription levels

Question 15

Which of the following best describes the role of general transcription factors in eukaryotic transcription?

Accepted Answer

They are required for the assembly of the pre-initiation complex at the promoter.

Question 16

Alternative splicing allows a single gene to:

Accepted Answer

Produce multiple protein isoforms with different functions.

Question 17

Which of the following mechanisms can regulate the steady-state level of mRNA in a cell?

Accepted Answer

The rate of mRNA degradation

Question 18

The p53 protein is rapidly degraded in normal cells. What molecular tag is added to p53 to target it for degradation by the proteasome?

Accepted Answer

Ubiquitin

Question 19

Which of the following is true regarding DNA methylation in vertebrates?

Accepted Answer

It silences gene expression by blocking transcription factor binding and recruiting proteins that remove acetyl groups.

Question 20

In the yeast GAL gene system, what is the function of the Gal4 protein?

Accepted Answer

It acts as an activator that binds to UASG and promotes transcription of GAL genes.

Genetic Mechanisms: Double-Strand Break Repair, Transposable Elements, and Regulation of Gene Expression

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