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 present in proteins but not in DNA, and phosphorus is present in DNA but not in proteins.

Question 2

A scientist isolates a nucleic acid and finds that it contains the bases adenine, guanine, cytosine, and uracil. Which type of molecule is this most likely to be?

Accepted Answer

RNA

Question 3

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

Accepted Answer

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

Question 4

What was the key finding of the Meselson-Stahl experiment regarding DNA replication?

Accepted Answer

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

Question 5

Which of the following best describes the difference between a purine and a pyrimidine?

Accepted Answer

Purines (adenine and guanine) have a double ring structure, while pyrimidines (cytosine and thymine) have a single ring structure.

Question 6

A mutation changes a DNA codon from $$	ext{GAA} to$$ $$	ext{GAG}$$, but both codons code for glutamic acid. What type of mutation is this?

Accepted Answer

Silent mutation

Question 7

During DNA replication, which enzyme is responsible for unwinding the double helix at the replication fork?

Accepted Answer

Helicase

Question 8

Which of the following best explains why a frameshift mutation early in an exon is more likely to disrupt protein function than a silent mutation in an intron?

Accepted Answer

Frameshift mutations change the reading frame, altering all downstream amino acids, while silent mutations in introns do not affect the coding sequence.

Question 9

Which of the following is NOT a difference between DNA and RNA?

Accepted Answer

DNA contains a poly-A tail, while RNA contains a 5’ cap.

Question 10

A mature mRNA transcript differs from pre-mRNA in which of the following ways?

Accepted Answer

Mature mRNA has a 5’ cap and poly-A tail, and lacks introns.

Question 11

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

Accepted Answer

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

Question 12

If a DNA strand has the sequence $$5'	ext{-ATCGGTA-}3'$$, what is the complementary RNA sequence produced during transcription?

Accepted Answer

$$3'	ext{-UAGCCAU-}5'$$

Question 13

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 14

Which enzyme is responsible for removing RNA primers and replacing them with DNA nucleotides during DNA replication?

Accepted Answer

DNA polymerase I

Question 15

A mutation changes a codon from $$	ext{UAC} ($$tyrosine) to $$	ext{UAA} ($$stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 16

Which of the following best describes the role of the spliceosome in eukaryotic cells?

Accepted Answer

It removes introns from pre-mRNA and joins exons together.

Question 17

Which of the following scenarios would most likely result in a frameshift mutation?

Accepted Answer

A single nucleotide insertion in an exon

Question 18

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

Accepted Answer

To ensure the DNA molecule has a uniform diameter.

Question 19

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 20

A patient has a mutation in the gene encoding a tRNA synthetase. Which process would be directly affected?

Accepted Answer

Attachment of amino acids to their corresponding tRNAs

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