Question 1

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

Each daughter DNA molecule consists of one parental strand and one newly synthesized strand.

Question 2

During DNA replication, which enzyme is responsible for synthesizing the new DNA strand by adding nucleotides to the growing chain?

Accepted Answer

DNA polymerase

Question 3

Why is a primer necessary for DNA replication, and what type of molecule is it?

Accepted Answer

It provides a free 3' hydroxyl group for DNA polymerase to begin synthesis; it is an RNA molecule.

Question 4

In eukaryotic cells, why is telomerase activity necessary in germ cells?

Accepted Answer

To prevent the progressive shortening of chromosome ends during DNA replication.

Question 5

Which of the following statements about the directionality of DNA replication is correct?

Accepted Answer

DNA synthesis always proceeds in the 5' to 3' direction.

Question 6

A mutation occurs in the promoter region of a gene. What is the most likely effect on gene expression?

Accepted Answer

Transcription initiation may be reduced or prevented, leading to decreased protein synthesis.

Question 7

Which of the following best explains why eukaryotic mRNA is processed before leaving the nucleus?

Accepted Answer

To remove introns, add a 5' cap, and a 3' poly-A tail, increasing mRNA stability and translation efficiency.

Question 8

If a tRNA has the anticodon 5' UGG 3', which codon(s) can it recognize due to the wobble effect, and which amino acid will it carry?

Accepted Answer

It can recognize codons 5' CCA 3' and 5' CCG 3', and will carry proline.

Question 9

Which type of mutation is most likely to result in a nonfunctional protein due to a premature stop codon?

Accepted Answer

Nonsense mutation

Question 10

In the lac operon of E. coli, what is the role of the inducer (allolactose)?

Accepted Answer

It binds to the repressor, causing it to release from the operator and allowing transcription.

Question 11

Which of the following best describes positive regulation of gene expression in prokaryotes?

Accepted Answer

A regulatory protein (such as CAP) binds DNA and increases the rate of transcription.

Question 12

How does histone acetylation affect gene expression in eukaryotic cells?

Accepted Answer

It loosens chromatin structure, making DNA more accessible for transcription.

Question 13

Which of the following is a plausible explanation for the coordination of gene expression in prokaryotes?

Accepted Answer

Functionally related genes are clustered together in operons and transcribed as a single mRNA.

Question 14

Which of the following best describes the principle of nucleic acid hybridization and its application in biotechnology?

Accepted Answer

Single-stranded DNA or RNA molecules can base-pair with complementary sequences, allowing detection or isolation of specific genes.

Question 15

During PCR (Polymerase Chain Reaction), why must primers be designed to run 5'-3' on both strands?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, so primers must provide a free 3' hydroxyl group.

Question 16

Which of the following best explains why shorter DNA fragments travel farther during gel electrophoresis?

Accepted Answer

Shorter fragments experience less resistance from the gel matrix and move more quickly toward the positive electrode.

Question 17

Which of the following is a key advantage of the CRISPR-Cas9 system in gene editing?

Accepted Answer

It allows for precise, targeted changes to the genome at specific DNA sequences.

Question 18

A patient receives gene therapy using a viral vector to deliver a functional copy of a gene. Which of the following best describes the goal of this therapy?

Accepted Answer

To replace or supplement a defective gene, restoring normal function.

Question 19

Which of the following statements about noncoding RNAs is correct?

Accepted Answer

They can regulate gene expression at multiple levels, including mRNA degradation and translation inhibition.

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