Question 1

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

Accepted Answer

A double-strand break is created, followed by end resection to generate 3' single-stranded overhangs.

Question 2

During the resolution of a Holliday junction, what determines whether a crossover or non-crossover product is formed?

Accepted Answer

The orientation of the cuts made by resolvase enzymes at the junction.

Question 3

Which of the following is a key difference between DNA transposons and retrotransposons?

Accepted Answer

DNA transposons move directly as DNA, while retrotransposons move via an RNA intermediate.

Question 4

A mutation in the F8 gene on the X chromosome is found to be caused by a LINE-1 (L1) insertion. Which process most likely led to this mutation?

Accepted Answer

Retrotransposition via target-primed reverse transcription.

Question 5

Which structural feature is essential for the recognition and excision of a DNA transposon by transposase?

Accepted Answer

Inverted terminal repeats (ITRs)

Question 6

In the synthesis-dependent strand annealing (SDSA) pathway of homologous recombination repair, what is the final outcome?

Accepted Answer

A non-crossover product with gene conversion.

Question 7

Which of the following best explains how transposable elements can cause chromosomal rearrangements such as inversions or translocations?

Accepted Answer

By providing homologous sequences that facilitate unequal crossing over or recombination.

Question 8

A researcher wants to use a transposon system to generate transgenic mice. Which of the following steps is essential for stable integration of the gene of interest?

Accepted Answer

Co-injection of transposase mRNA or DNA with the transposon containing the gene of interest.

Question 9

Which of the following is a characteristic of SINE elements in the human genome?

Accepted Answer

They are non-autonomous and use LINE machinery for retrotransposition.

Question 10

What is the role of reverse transcriptase in the life cycle of a retrotransposon?

Accepted Answer

It synthesizes a DNA copy (cDNA) from the retrotransposon RNA.

Question 11

A Drosophila mutant with orange-yellow eyes is found to have a copia element inserted in the second intron of the white gene. What is the most likely molecular consequence of this insertion?

Accepted Answer

Premature termination of mRNA due to the polyadenylation signal in the copia element.

Question 12

Which of the following best describes the function of direct repeats (DRs) flanking a transposable element?

Accepted Answer

They are created during insertion and mark the boundaries of the insertion site.

Question 13

Which of the following equations correctly represents the process of reverse transcription by reverse transcriptase?

Accepted Answer

$$RNA \xrightarrow{	ext{reverse transcriptase}} cDNA$$

Question 14

Which of the following is a potential evolutionary benefit of transposable elements in a genome?

Accepted Answer

They provide raw material for adaptation by generating genetic diversity.

Question 15

In the context of homologous recombination, what is a D-loop?

Accepted Answer

A structure formed when a single DNA strand invades a double helix and displaces one of its strands.

Question 16

Which of the following best explains why homologous recombination repair (HRR) is restricted to the S and G2 phases of the cell cycle?

Accepted Answer

A sister chromatid is available as a template only after DNA replication.

Question 17

Which of the following is a correct description of the 'cut-and-paste' mechanism of DNA transposons?

Accepted Answer

The transposon is excised from its original location and inserted directly into a new site in the genome.

Question 18

Which of the following best describes the role of integrase in retrotransposon movement?

Accepted Answer

It inserts the newly synthesized cDNA into the host genome.

Question 19

A student is studying a non-autonomous DNA transposon. Which of the following statements is most accurate?

Accepted Answer

It requires the transposase encoded by an autonomous element for movement.

Homologous Recombination Repair and Transposable Elements: Mechanisms and Genetic Impact

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