Question 1

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

Accepted Answer

Hershey and Chase's use of radioactive isotopes in T2 phage infection

Question 2

A DNA molecule has 20% adenine. According to Chargaff's rules, what percentage of guanine does it contain?

Accepted Answer

$$30\%$$

Question 3

Which of the following best describes the directionality of DNA synthesis by DNA polymerase?

Accepted Answer

It synthesizes DNA in the $$5' \rightarrow 3'$$ direction by adding nucleotides to the $$3'$$ end.

Question 4

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

Accepted Answer

Nonsense mutation

Question 5

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

Accepted Answer

DNA gyrase (topoisomerase)

Question 6

A bacterial cell has a mutation in the lacI gene resulting in a nonfunctional repressor protein. What is the most likely outcome for the lac operon?

Accepted Answer

The lac operon will be constitutively expressed, regardless of lactose presence.

Question 7

Which of the following statements about the genetic code is FALSE?

Accepted Answer

It is overlapping, so each nucleotide is part of more than one codon.

Question 8

Which process is responsible for removing introns from pre-mRNA in eukaryotes?

Accepted Answer

Splicing by the spliceosome

Question 9

A patient has a mutation in the gene encoding telomerase, resulting in a nonfunctional enzyme. What is the most likely cellular consequence?

Accepted Answer

Chromosome ends will progressively shorten with each cell division.

Question 10

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

Accepted Answer

DNA polymerase can only synthesize DNA in the $$5' \rightarrow 3'$$ direction, but the lagging strand template is oriented $$5' \rightarrow 3'$$ away from the fork.

Question 11

A DNA sample is subjected to increasing temperature. What is the most likely outcome as the temperature rises?

Accepted Answer

Hydrogen bonds between bases break, leading to DNA denaturation.

Question 12

Which of the following is a property of the trp operon attenuation mechanism in bacteria?

Accepted Answer

It terminates transcription prematurely when tryptophan is abundant.

Question 13

A DNA sequence is mutated from $$5'	ext{-}ATG\,GCC\,TAA\,GGA\,TGA\,3' to$$ $$5'	ext{-}ATG\,GCC\,TGA\,GGA\,TGA\,3'. $$What is the effect of this mutation?

Accepted Answer

A nonsense mutation causing premature termination.

Question 14

Which of the following best describes the function of small regulatory RNAs in bacteria?

Accepted Answer

They bind to mRNA to regulate translation or stability.

Question 15

A patient is exposed to a mutagen that causes the insertion of a single nucleotide into a coding sequence. What is the most likely result?

Accepted Answer

A frameshift mutation

Question 16

Which of the following is TRUE regarding the difference between prokaryotic and eukaryotic translation?

Accepted Answer

Prokaryotic translation can begin before transcription is finished.

Question 17

Which of the following best describes the role of the CAP-cAMP complex in the regulation of the lac operon?

Accepted Answer

It activates the lac operon when glucose is low and cAMP is high.

Question 18

A DNA repair system recognizes and removes uracil from DNA. Which repair pathway is most likely involved?

Accepted Answer

Base excision repair

Question 19

Which of the following is a key difference between DNA and RNA molecules?

Accepted Answer

DNA contains deoxyribose, while RNA contains ribose.

Question 20

A gene mutation occurs in a somatic cell and is not passed to offspring. What type of mutation is this?

Accepted Answer

Non-heritable mutation

Genetics Exam 2 Study Guide: DNA Structure, Replication, Transcription, Translation, Mutation, and Gene Regulation

Study Guide - Practice Questions

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