Question 1

Which of the following best describes the relationship between genotype and phenotype in a bacterial cell?

Accepted Answer

Genotype is the genetic makeup, and phenotype is the expression of those genes as observable traits.

Question 2

During DNA replication in bacteria, which enzyme is responsible for joining Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 3

A mutation changes a single base in a gene from cytosine (C) to adenine (A). Which process will ultimately determine if this mutation affects the phenotype of the organism?

Accepted Answer

Translation, because it interprets the mRNA codons and may result in a different amino acid sequence.

Question 4

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

Accepted Answer

The genetic code is universal and consists of codons, each made up of three nucleotides.

Question 5

In eukaryotic cells, what is the correct sequence of events for gene expression from DNA to protein?

Accepted Answer

Transcription → RNA processing → Translation

Question 6

A researcher discovers a bacterial operon that is normally off but can be turned on in the presence of a specific sugar. What type of operon is this, and what is a classic example?

Accepted Answer

Inducible operon; example: lac operon

Question 7

Which enzyme is responsible for relaxing supercoiled DNA ahead of the replication fork during bacterial DNA replication?

Accepted Answer

Topoisomerase (or DNA gyrase)

Question 8

A mutation in the gene encoding RNA polymerase in a bacterium prevents it from binding to the promoter. What is the most likely consequence?

Accepted Answer

Transcription of the gene will not initiate.

Question 9

Which of the following best explains why transcription and translation can occur simultaneously in prokaryotes but not in eukaryotes?

Accepted Answer

Prokaryotes lack a nuclear membrane, so ribosomes can access mRNA as it is being transcribed.

Question 10

A scientist is studying a eukaryotic gene and observes that the initial RNA transcript is longer than the final mRNA. What process accounts for this difference?

Accepted Answer

Removal of introns during RNA processing

Question 11

Which of the following is NOT a function of DNA polymerase during DNA replication?

Accepted Answer

Joining Okazaki fragments together

Question 12

A bacterial cell is exposed to an inducer molecule that binds to a repressor protein, causing it to release from the operator region of an operon. What is the immediate effect on gene expression?

Accepted Answer

Transcription of the operon's structural genes increases.

Question 13

Which of the following base-pairing rules is correct for DNA?

Accepted Answer

Adenine pairs with thymine, and cytosine pairs with guanine.

Question 14

A mutation in a bacterial cell prevents the production of primase. Which step of DNA replication will be directly affected?

Accepted Answer

Synthesis of RNA primers

Question 15

Which of the following best describes the structure of a typical bacterial genome?

Accepted Answer

A single circular DNA chromosome with protein-encoding and noncoding regions

Question 16

A patient is diagnosed with a genetic disorder caused by a defect in the removal of introns from pre-mRNA. Which cellular component is most likely malfunctioning?

Accepted Answer

Small nuclear ribonucleoproteins (snRNPs)

Question 17

Which of the following equations best represents the semiconservative model of DNA replication?

Accepted Answer

$$	ext{Parent DNA} ightarrow 	ext{1 old strand} + 	ext{1 new strand}$$

Question 18

A mutation in the operator region of a repressible operon prevents the repressor protein from binding, even in the presence of a corepressor. What is the likely outcome?

Accepted Answer

The operon's genes will be continuously transcribed.

Question 19

Which of the following is a correct description of the function of tRNA during translation?

Accepted Answer

tRNA brings amino acids to the ribosome and matches its anticodon to the mRNA codon.

Question 20

A bacterial cell is exposed to a drug that inhibits DNA gyrase. Predict the most immediate effect on DNA replication.

Accepted Answer

Supercoiling ahead of the replication fork will prevent efficient DNA replication.

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