Question 1

Which of the following best describes the antiparallel nature of DNA strands in the double helix?

Accepted Answer

One strand runs 5' to 3' and the other runs 3' to 5'.

Question 2

During DNA replication, why is the lagging strand synthesized in short fragments known as Okazaki fragments?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, and the lagging strand template is oriented 5' to 3'.

Question 3

Which enzyme is responsible for joining Okazaki fragments during DNA replication?

Accepted Answer

DNA ligase

Question 4

A mutation changes a codon from $$	ext{UAC} to$$ $$	ext{UAA}. $$What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; results in premature termination of translation

Question 5

Which of the following best explains why the RNA primer at the 5' end of the leading strand cannot be replaced with DNA nucleotides?

Accepted Answer

DNA polymerase cannot add nucleotides to the 5' end because there is no free 3' hydroxyl group.

Question 6

Which of the following best describes the function of a telomere?

Accepted Answer

It protects the ends of chromosomes from deterioration and fusion.

Question 7

A scientist treats cells with a chemical that prevents histone acetylation. What is the most likely effect on gene expression?

Accepted Answer

Decreased transcription due to tighter chromatin packing

Question 8

Which of the following statements about the genetic code is correct?

Accepted Answer

The code is redundant; multiple codons can specify the same amino acid.

Question 9

During transcription, which of the following correctly describes the role of the promoter region?

Accepted Answer

It is the site where RNA polymerase and transcription factors bind to initiate transcription.

Question 10

Which of the following best describes the difference between heterochromatin and euchromatin?

Accepted Answer

Heterochromatin is more condensed and transcriptionally inactive; euchromatin is less condensed and active.

Question 11

A patient is found to have a mutation in a gene that results in the removal of a single nucleotide, shifting the reading frame. What type of mutation is this, and what is its likely effect?

Accepted Answer

Frameshift mutation; likely results in a nonfunctional protein

Question 12

Which of the following best describes the function of microRNAs (miRNAs) in gene regulation?

Accepted Answer

They degrade or block translation of target mRNAs.

Question 13

Which of the following is a function of the proteasome in eukaryotic cells?

Accepted Answer

Degrading and recycling damaged or unneeded proteins

Question 14

In the lac operon of E. coli, what is the function of the operator region?

Accepted Answer

It binds the repressor protein to regulate transcription.

Question 15

Which of the following best explains the difference between repressible and inducible operons?

Accepted Answer

Repressible operons are usually on and can be turned off; inducible operons are usually off and can be turned on.

Question 16

A gene is transcribed and produces a primary RNA transcript containing both introns and exons. Which process removes the introns and joins the exons?

Accepted Answer

Splicing by the spliceosome

Question 17

Which of the following best describes the role of tRNA during translation?

Accepted Answer

tRNA carries amino acids to the ribosome and matches its anticodon to the mRNA codon.

Question 18

Which of the following is a direct result of alternative RNA splicing?

Accepted Answer

A single gene can produce multiple protein variants.

Question 19

A researcher finds that a gene is not being transcribed even though the promoter is intact. Which of the following could explain this observation?

Accepted Answer

Specific transcription factors required for activation are missing.

Question 20

Which of the following best describes epigenetic inheritance?

Accepted Answer

Inheritance of traits due to changes in gene expression not involving changes in DNA sequence

Comprehensive Guidance for DNA, Gene Expression, and Regulation Study Questions

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