Question 1

Which of the following best explains why sulfur and phosphorus were chosen as radioactive labels in the Hershey-Chase experiment?

Accepted Answer

Sulfur is found in proteins but not DNA, and phosphorus is found in DNA but not proteins.

Question 2

Which of the following statements about the structure of DNA is correct?

Accepted Answer

Adenine always pairs with thymine via hydrogen bonds, and the strands are antiparallel.

Question 3

What was the key finding from Rosalind Franklin’s X-ray crystallography data that helped Watson and Crick determine the structure of DNA?

Accepted Answer

DNA is a double helix with a consistent diameter.

Question 4

Which of the following best describes the difference between purines and pyrimidines in DNA?

Accepted Answer

Purines (A and G) are double-ringed, while pyrimidines (C and T) are single-ringed.

Question 5

Why must a purine always pair with a pyrimidine in the DNA double helix?

Accepted Answer

To ensure the DNA molecule has a consistent diameter.

Question 6

Which enzyme is responsible for unwinding the DNA double helix during replication?

Accepted Answer

Helicase

Question 7

During DNA replication, which enzyme synthesizes short RNA primers to provide a starting point for DNA polymerase?

Accepted Answer

Primase

Question 8

A mutation changes a codon from UAU to UAA. What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; introduces a premature stop codon

Question 9

Which of the following best describes the difference between pre-mRNA and mature mRNA in eukaryotic cells?

Accepted Answer

Pre-mRNA contains introns, while mature mRNA has had introns removed and has a 5’ cap and poly-A tail.

Question 10

Which of the following statements about the Meselson-Stahl experiment is correct?

Accepted Answer

It showed that DNA replication is semiconservative, with each new DNA molecule containing one old and one new strand.

Question 11

Which of the following best explains why the genetic code is described as 'degenerate' or 'redundant'?

Accepted Answer

Multiple codons can code for the same amino acid.

Question 12

A DNA strand has the sequence 5’-ATGCCGTA-3’. What is the complementary DNA sequence (written 5’ to 3’)?

Accepted Answer

5’-TACGGCAT-3’

Question 13

Which of the following mutations is most likely to have the least effect on the function of a protein?

Accepted Answer

A silent mutation in an exon

Question 14

Which of the following best describes the function of DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments together on the lagging strand.

Question 15

Which of the following is a difference between DNA and RNA?

Accepted Answer

DNA is usually double-stranded, while RNA is usually single-stranded.

Question 16

A mutation causes the insertion of a single nucleotide early in the coding region of a gene. What is the most likely result?

Accepted Answer

A frameshift mutation

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 codon on mRNA.

Question 18

Which of the following is true about the directionality of nucleic acids?

Accepted Answer

The 5’ end has a free phosphate group, and the 3’ end has a free -OH group.

Question 19

Which of the following best describes the function of the spliceosome?

Accepted Answer

It removes introns from pre-mRNA.

Molecular Biology of the Gene: Structure, Replication, and Expression

Study Guide - Practice Questions