Question 1

Which of the following best describes the outcome of Griffith's critical experiment involving Streptococcus pneumoniae and mice?

Accepted Answer

Mice injected with living IIR and heat-killed IIS died, and living IIS was recovered.

Question 2

Which of the following statements is NOT consistent with Chargaff’s rules?

Accepted Answer

$$(C + G) = (A + T)$$

Question 3

What is the significance of the melting temperature ($$T_m) in $$DNA studies?

Accepted Answer

It is the temperature at which 50% of the DNA strands have denatured.

Question 4

A nucleotide with the structure shown (with an OH group at the 2' position of the sugar) is most likely found in:

Accepted Answer

RNA; purine

Question 5

If the chemical group labeled (X) in a nucleotide is H and (Y) is OH, this molecule is:

Accepted Answer

A deoxyribonucleotide in DNA

Question 6

Which enzyme is responsible for relieving the supercoiling tension ahead of the replication fork during DNA replication?

Accepted Answer

DNA gyrase (a type of topoisomerase)

Question 7

Which DNA polymerase in E. coli is primarily responsible for removing RNA primers and filling in the resulting gaps?

Accepted Answer

DNA polymerase I

Question 8

During DNA replication, which strand is synthesized discontinuously and why?

Accepted Answer

The lagging strand, because DNA polymerase can only synthesize in the 5' to 3' direction.

Question 9

Which of the following best explains the semiconservative model of DNA replication?

Accepted Answer

Each new DNA molecule consists of one old and one new strand.

Question 10

In the Meselson-Stahl experiment, what would be the expected result after two generations if DNA replication were dispersive?

Accepted Answer

One band at intermediate density, but broader than after one generation

Question 11

Which enzyme synthesizes the short RNA primer required for DNA polymerase to initiate DNA synthesis?

Accepted Answer

Primase

Question 12

What is the primary function of single-stranded binding proteins (SSBPs) during DNA replication?

Accepted Answer

To stabilize the open conformation of single-stranded DNA

Question 13

Which of the following is a direct consequence of the end-replication problem in eukaryotic cells?

Accepted Answer

Chromosomes shorten with each cell division.

Question 14

Telomerase is most active in which type of cells?

Accepted Answer

Stem cells and malignant (cancer) cells

Question 15

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

Accepted Answer

It joins Okazaki fragments by forming phosphodiester bonds.

Question 16

A mutation in the gene encoding DNA polymerase III that eliminates its 3' to 5' exonuclease activity would most likely result in:

Accepted Answer

Increased mutation rate due to loss of proofreading

Question 17

Which of the following is NOT a challenge that must be resolved during DNA replication?

Accepted Answer

Translation of mRNA into protein

Question 18

Which property is unique to DNA polymerase I among the bacterial DNA polymerases?

Accepted Answer

5' to 3' exonuclease activity

Question 19

Why are telomeres composed of repetitive DNA sequences?

Accepted Answer

To protect chromosome ends from degradation and fusion

Question 20

Which of the following best explains why DNA polymerase cannot initiate DNA synthesis de novo?

Accepted Answer

It requires a free 3'-OH group provided by a primer.

Genetics Homework Review: DNA Structure and Replication Study Guide

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