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 in E. coli?

Accepted Answer

DNA gyrase (topoisomerase II)

Question 6

A patient has a mutation in the gene encoding the lac repressor (lacI) that prevents it from binding to the operator. What is the most likely effect on the lac operon?

Accepted Answer

The 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

Spliceosome-mediated splicing

Question 9

A DNA sample is heated to $$95^\circC $$and then slowly cooled in the presence of a complementary DNA strand. What process is occurring during the cooling phase?

Accepted Answer

Hybridization

Question 10

If a gene contains the sequence $$5'	ext{-}ATG\,GCC\,TAA\,GGA\,TGA	ext{-}3'$$, how many amino acids will be translated from this gene (assuming the first ATG is the start codon and TAA/TGA are stop codons)?

Accepted Answer

2

Question 11

Which of the following best explains why telomerase activity is important in stem cells but not in most somatic cells?

Accepted Answer

Telomerase extends telomeres, allowing stem cells to divide many times without losing genetic information.

Question 12

Which of the following is a key difference between prokaryotic and eukaryotic translation?

Accepted Answer

Eukaryotic mRNAs are typically monocistronic, while prokaryotic mRNAs can be polycistronic.

Question 13

A mutation changes the DNA sequence $$5'	ext{-}GAA	ext{-}3' ($$which codes for glutamic acid) to $$5'	ext{-}GAG	ext{-}3'. $$What type of mutation is this?

Accepted Answer

Silent mutation

Question 14

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

Accepted Answer

It activates transcription of the lac operon when glucose is low.

Question 15

Which of the following is TRUE regarding Okazaki fragments?

Accepted Answer

They are joined together by DNA ligase.

Question 16

A bacterial cell is exposed to a mutagen that causes insertions of a single nucleotide in coding regions. What is the most likely effect on the resulting protein?

Accepted Answer

A frameshift mutation that alters the reading frame.

Question 17

Which of the following is a regulatory RNA that can inhibit translation in bacteria?

Accepted Answer

Small RNA (sRNA)

Question 18

In the trp operon, what is the effect of attenuation when tryptophan levels are high?

Accepted Answer

Transcription is prematurely terminated, reducing trp operon expression.

Question 19

Which of the following best describes the role of the 5' cap and poly-A tail in eukaryotic mRNA?

Accepted Answer

They protect mRNA from degradation and aid in translation initiation.

Question 20

A patient inherits a mutation in a DNA repair gene, leading to increased cancer risk. This mutation is best described as:

Accepted Answer

A heritable (germline) mutation

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

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