Question 1

Which experiment provided the first direct evidence that DNA is the genetic material responsible for heredity in cells?

Accepted Answer

Avery, MacLeod, and McCarty's transformation experiment

Question 2

During DNA replication, which enzyme is responsible for synthesizing the majority of the new DNA strand by adding nucleotides to the 3' end?

Accepted Answer

DNA polymerase III

Question 3

Which base pairs with cytosine in the DNA double helix, and what type of bond holds them together?

Accepted Answer

Guanine, held by three hydrogen bonds

Question 4

Which model of DNA replication was supported by the Meselson-Stahl experiment, and what was the key result?

Accepted Answer

Semiconservative; each daughter DNA contains one parental and one new strand

Question 5

What is the primary function of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments on the lagging strand

Question 6

A mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 7

Which enzyme prevents supercoiling ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 8

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

Accepted Answer

They prevent the separated DNA strands from reannealing

Question 9

Which repair mechanism specifically removes bulky DNA lesions, such as thymine dimers caused by UV light?

Accepted Answer

Nucleotide excision repair

Question 10

During DNA replication, nucleotides are always added to which end of the growing DNA strand?

Accepted Answer

3' end

Question 11

Which of the following best describes Okazaki fragments?

Accepted Answer

Short DNA segments synthesized on the lagging strand

Question 12

A cell accumulates mutations because it cannot correct mismatched base pairs that occur during DNA replication. Which repair system is likely defective?

Accepted Answer

Mismatch repair

Question 13

Which enzyme extends the ends of eukaryotic chromosomes to prevent loss of genetic information during replication?

Accepted Answer

Telomerase

Question 14

Which of the following is a correct description of a frameshift mutation?

Accepted Answer

A mutation caused by insertion or deletion of nucleotides that alters the reading frame

Question 15

Which stage of cell signaling involves the binding of a signaling molecule to its receptor?

Accepted Answer

Reception

Question 16

Which type of cell signaling involves a cell releasing a signal that affects only nearby cells, but not itself?

Accepted Answer

Paracrine signaling

Question 17

Endocrine signaling is characterized by which of the following?

Accepted Answer

Release of hormones into the bloodstream to affect distant cells

Question 18

Which of the following best describes a ligand in cell signaling?

Accepted Answer

A molecule that binds to a receptor to initiate a cellular response

Question 19

A cell receives a signal that causes a rapid change in ion concentration, but no change in gene expression. This is an example of which type of response?

Accepted Answer

Short-term response

Question 20

Which of the following equations correctly represents the complementary base pairing in DNA?

Accepted Answer

$$A = T, G = C$$

DNA Structure, Function, and Cell Communication: Study Guide

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