Question 1

Which of the following best explains why DNA strands are described as 'antiparallel'?

Accepted Answer

The two strands run in opposite directions: one from 5’ to 3’ and the other from 3’ to 5’.

Question 2

During DNA replication, why is primase required for the synthesis of new DNA strands?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3’-OH group, which primase provides by synthesizing a short RNA primer.

Question 3

A mutation occurs in a gene’s promoter region, causing the promoter to be reversed in orientation. What is the most likely consequence?

Accepted Answer

The gene will be transcribed from the opposite DNA strand, potentially producing a nonfunctional protein.

Question 4

Given the following DNA template strand: 3’-TACGGTACG-5’, what is the corresponding mRNA sequence?

Accepted Answer

5’-AUGCCAUGC-3’

Question 5

Which of the following best describes the role of the 5’ cap in eukaryotic mRNA?

Accepted Answer

It protects mRNA from degradation and assists in ribosome binding during translation.

Question 6

Alternative splicing of pre-mRNA allows for which of the following?

Accepted Answer

A single gene to produce multiple protein isoforms.

Question 7

A scientist is analyzing a segment of DNA and finds that one strand is being synthesized continuously while the other is synthesized in short fragments. Which strand is the lagging strand?

Accepted Answer

The strand synthesized in short fragments away from the replication fork.

Question 8

Which of the following mechanisms helps prevent mutations during DNA replication?

Accepted Answer

Proofreading activity of DNA polymerase, which removes incorrectly paired nucleotides.

Question 9

Given the mRNA sequence 5’-AUGGCCUAA-3’, what is the resulting amino acid sequence? (Use the standard genetic code.)

Accepted Answer

Met-Ala-Stop

Question 10

Which of the following best explains how the same DNA sequence can result in different cell types in a multicellular organism?

Accepted Answer

Different genes are expressed in different cells due to regulatory mechanisms controlling gene accessibility and expression.

Question 11

Which of the following statements about the stability of RNA compared to DNA is correct?

Accepted Answer

RNA is less stable than DNA due to the presence of a 2’-OH group in its ribose sugar.

Question 12

During translation, where does peptide bond formation occur?

Accepted Answer

In the ribosome’s large subunit between the amino acids attached to tRNAs in the P and A sites.

Question 13

Which of the following is a function of the poly(A) tail added to eukaryotic mRNA?

Accepted Answer

It increases mRNA stability and facilitates export from the nucleus.

Question 14

A regulatory protein binds to a DNA sequence and increases the rate of transcription of a nearby gene. This protein is best described as:

Accepted Answer

An activator.

Question 15

Which of the following scenarios best illustrates post-translational regulation of gene expression?

Accepted Answer

A protein is phosphorylated, altering its activity after translation.

Question 16

If a DNA sequence is tightly wrapped around histones and not accessible to transcription factors, what is the likely effect on gene expression?

Accepted Answer

Transcription of the gene will be reduced or silenced.

Question 17

Which of the following best describes the 'RNA world' hypothesis?

Accepted Answer

RNA was likely the first hereditary molecule, capable of both storing genetic information and catalyzing chemical reactions.

Question 18

A mutation changes a single base in a DNA coding strand from G to A. What is the potential effect on the resulting protein?

Accepted Answer

It could result in a different amino acid, a premature stop codon, or no change at all, depending on the codon affected.

Question 19

Which of the following is necessary to determine the correct reading frame of an mRNA sequence?

Accepted Answer

Identifying the position of the start codon (AUG).

Question 20

Which of the following is an example of post-transcriptional regulation?

Accepted Answer

Alternative splicing of pre-mRNA to produce different mRNAs from the same gene.

DNA, RNA, and Gene Expression: Study Guide for Exam 3

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