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 based on Rosalind Franklin’s X-ray crystallography findings?

Accepted Answer

DNA is a double helix with a consistent diameter between the two strands.

Question 3

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

Accepted Answer

Purines (A and G) have a double ring structure, while pyrimidines (C and T) have a single ring structure.

Question 4

If a DNA molecule contains 30% adenine, according to Chargaff’s rules, what percentage of cytosine would you expect?

Accepted Answer

$$20\%$$

Question 5

Which of the following best explains why a purine-purine or pyrimidine-pyrimidine base pair would disrupt the structure of DNA?

Accepted Answer

Purine-purine pairs are too large, and pyrimidine-pyrimidine pairs are too small, disrupting the consistent diameter of the helix.

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 synthesis?

Accepted Answer

Primase

Question 8

A mutation changes a codon from $$UAC to$$ $$UAA. $$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 genetic code is correct?

Accepted Answer

The genetic code is degenerate, meaning multiple codons can code for the same amino acid.

Question 11

A scientist observes that after one round of DNA replication in the Meselson-Stahl experiment, all DNA molecules have intermediate density. What does this observation support?

Accepted Answer

The semiconservative model of DNA replication

Question 12

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

Accepted Answer

Joins Okazaki fragments on the lagging strand

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 is a correct pairing of complementary bases in DNA?

Accepted Answer

Adenine and thymine

Question 15

Which of the following best describes the directionality of a DNA strand?

Accepted Answer

The 5’ end has a phosphate group, and the 3’ end has a hydroxyl group.

Question 16

Which of the following statements about RNA is correct?

Accepted Answer

RNA is typically single-stranded and contains uracil instead of thymine.

Question 17

A mutation occurs in the third position of a codon, but the amino acid sequence does not change. What is this an example of?

Accepted Answer

Silent mutation

Question 18

Which of the following best explains why the genetic code is described as 'universal'?

Accepted Answer

All organisms use the same codons to specify the same amino acids.

Question 19

Which of the following enzymes removes RNA primers and replaces them with DNA nucleotides during DNA replication?

Accepted Answer

DNA polymerase I

Question 20

A patient has a mutation in the gene encoding a spliceosome component. Which of the following is a likely consequence?

Accepted Answer

Mature mRNA will retain introns, potentially leading to nonfunctional proteins.

Molecular Biology of the Gene: Structure, Replication, Transcription, Translation, and Mutations

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