Question 1

Which of the following best describes the difference between the pentose sugars found in DNA and RNA?

Accepted Answer

DNA contains deoxyribose, which lacks an oxygen atom on the 2' carbon, while RNA contains ribose, which has an oxygen atom on the 2' carbon.

Question 2

In a DNA molecule, the covalent bond that links adjacent nucleotides is formed between which two groups?

Accepted Answer

The —OH group on the 3' carbon of one nucleotide and the phosphate group on the 5' carbon of the next.

Question 3

Which enzyme is responsible for unwinding the DNA double helix at the origin of replication?

Accepted Answer

Helicase

Question 4

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

Accepted Answer

Because DNA polymerase can only add nucleotides to the 3' end, and the lagging strand runs in the opposite direction, requiring synthesis in short segments called Okazaki fragments.

Question 5

What is the function of single-strand binding proteins during DNA replication?

Accepted Answer

They prevent the DNA strands from coming together again after being separated.

Question 6

Which of the following statements about DNA polymerase is correct?

Accepted Answer

DNA polymerase adds nucleotides only to the 3' end of a growing DNA strand.

Question 7

The sequence of bases in a DNA strand determines which of the following?

Accepted Answer

The primary structure of a protein.

Question 8

Which of the following best explains the semi-conservative model of DNA replication?

Accepted Answer

Each daughter DNA molecule contains one old strand from the parent and one newly synthesized strand.

Question 9

What is the role of DNA ligase during DNA replication?

Accepted Answer

It joins short segments of DNA to form continuous strands.

Question 10

Which of the following is a correct description of telomeres?

Accepted Answer

Telomeres are multiple repetitions of a short nucleotide sequence at each end of a eukaryotic chromosome that protect genes from erosion.

Question 11

Why do telomeres shorten with each cell division in most somatic cells?

Accepted Answer

Because DNA polymerase cannot replicate the very end of the lagging strand due to the absence of a primer.

Question 12

Which enzyme is responsible for lengthening telomeres in eukaryotic germ cells?

Accepted Answer

Telomerase

Question 13

A DNA strand has the sequence 5'–TTAGGGTTAGGGTTAGGG–3'. What is the complementary sequence on the opposite strand?

Accepted Answer

3'–AATCCCAATCCCAATCCC–5'

Question 14

If a human cell loses about 100 base pairs from its telomeric DNA during each mitotic division, how many TTAGGG repeats are lost per division?

Accepted Answer

About 16 repeats

Question 15

Which of the following is NOT a function of DNA polymerase?

Accepted Answer

Joining Okazaki fragments together

Question 16

Why is telomerase not active in most somatic cells, and what is the consequence?

Accepted Answer

Because telomerase is only active in germ cells; its absence in somatic cells leads to telomere shortening and eventual cell death.

Question 17

Which of the following best explains the 'end replication problem' in eukaryotic cells?

Accepted Answer

DNA polymerase cannot replicate the very end of linear chromosomes, resulting in progressive telomere shortening.

Question 18

Which of the following statements about Dolly the sheep and telomeres is correct?

Accepted Answer

Dolly's telomeres were only 80% as long as those in a normal one-year-old sheep, likely due to the absence of telomerase in the donor cell.

Question 19

During DNA replication, what is the direction in which the daughter DNA strand can grow?

Accepted Answer

5' → 3'

Molecular Biology of the Gene: DNA Structure and Replication

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