Question 1

Which experiment provided the first direct evidence that DNA, not protein, is the genetic material in bacteriophages?

Accepted Answer

Hershey-Chase experiment

Question 2

A researcher is cloning a gene into a plasmid vector. She digests both the vector and the insert with EcoRI, which produces sticky ends. What is the main advantage of using sticky ends in this process?

Accepted Answer

Sticky ends facilitate complementary base pairing, increasing the efficiency of ligation by DNA ligase.

Question 3

Which of the following statements about DNA replication is correct?

Accepted Answer

DNA polymerase adds nucleotides to the 3′ OH end, synthesizing DNA in the 5′ → 3′ direction.

Question 4

A mutation changes a codon from AAA (lysine) to AAG (also lysine). What type of mutation is this?

Accepted Answer

Silent mutation

Question 5

During DNA replication, what is the role of primase?

Accepted Answer

Primase synthesizes short RNA primers to provide a 3′ OH for DNA polymerase.

Question 6

A bacterial cell is exposed to DNA from its environment and acquires a new genetic trait. What is this process called?

Accepted Answer

Transformation

Question 7

Which repair pathway is primarily responsible for removing UV-induced thymine dimers?

Accepted Answer

Nucleotide excision repair (NER)

Question 8

A restriction enzyme recognizes the sequence 5′-GAATTC-3′ and cuts between G and A, producing sticky ends. What is the sequence of the overhang produced?

Accepted Answer

5′-AATT-3′

Question 9

If a circular plasmid is cut with a restriction enzyme that has two recognition sites, how many DNA fragments will be produced?

Accepted Answer

Two

Question 10

Which of the following best describes the difference between a nucleoside and a nucleotide?

Accepted Answer

A nucleoside contains only a sugar and base; a nucleotide contains a sugar, base, and phosphate.

Question 11

A DNA fragment is run on an agarose gel. Which fragment will migrate the farthest?

Accepted Answer

The smallest fragment

Question 12

Which of the following is a function of the tumor suppressor gene TP53?

Accepted Answer

Activates apoptosis and cell-cycle arrest when DNA damage is detected

Question 13

Which of the following equations correctly predicts the expected frequency of a 6-base restriction site in random DNA?

Accepted Answer

$$4^6 = 4096$

Question 14

A DNA polymerase incorporates an incorrect nucleotide during replication. Which enzymatic activity allows the polymerase to remove this mistake?

Accepted Answer

3′ → 5′ exonuclease activity

Question 15

Which of the following best explains why the lagging strand is synthesized discontinuously?

Accepted Answer

The lagging strand template runs 5′ → 3′, so DNA polymerase must synthesize short fragments in the 5′ → 3′ direction.

Question 16

Which of the following is NOT a mechanism of horizontal gene transfer in bacteria?

Accepted Answer

Transfection

Question 17

A patient with xeroderma pigmentosum is extremely sensitive to sunlight. Which DNA repair pathway is defective in this disorder?

Accepted Answer

Nucleotide excision repair (NER)

Question 18

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

Accepted Answer

DNA ligase creates covalent phosphodiester bonds to join DNA fragments.

Question 19

A restriction enzyme produces blunt ends. Which of the following statements is true about blunt-end ligation?

Accepted Answer

Blunt ends are less favorable for ligation because they lack complementary overhangs.

Question 20

Which of the following best describes semiconservative DNA replication?

Accepted Answer

Each daughter DNA molecule contains one original strand and one newly synthesized strand.

Molecular Genetics: Comprehensive Study Guide for College Genetics

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