Question 1

A bacterial cell is unable to synthesize tRNA due to a genetic mutation. Which of the following would be the most immediate consequence for the cell?

Accepted Answer

It would be unable to synthesize proteins.

Question 2

In a laboratory experiment, the necessary ingredients for DNA synthesis are mixed in a test tube. The DNA polymerase is from Thermus aquaticus, and the template is from a human cell. The DNA synthesized in this reaction would be most similar to:

Accepted Answer

Human DNA

Question 3

Why does a new DNA strand only elongate in the 5' to 3' direction during DNA replication?

Accepted Answer

Because DNA polymerase adds nucleotides only to the free 3' end.

Question 4

If cytosine makes up 38% of the nucleotides in a DNA sample, what percentage of the nucleotides will be thymine?

Accepted Answer

$12\%$

Question 5

Which of the following statements about the structure of nucleic acids is correct?

Accepted Answer

The backbone consists of alternating sugar and phosphate molecules.

Question 6

During DNA replication, which enzyme is responsible for synthesizing a short stretch of RNA to initiate polymerization?

Accepted Answer

Primase

Question 7

Which of the following mechanisms ensures the accuracy of DNA replication?

Accepted Answer

All of the above

Question 8

A mutation occurs that prevents the formation of hydrogen bonds between bases in DNA. What is the most likely consequence?

Accepted Answer

The DNA double helix would not form properly.

Question 9

Which of the following is NOT found in prokaryotic messenger RNA (mRNA)?

Accepted Answer

Intron

Question 10

A gene is best defined as:

Accepted Answer

A sequence of nucleotides in DNA that codes for a functional product.

Question 11

During the process of transcription in a eukaryotic cell, where does RNA polymerase bind to initiate transcription?

Accepted Answer

Promoter region

Question 12

Which of the following statements about ribosomes is FALSE?

Accepted Answer

The ribosomes of prokaryotes and eukaryotes are the same in structure and function.

Question 13

Which of the following best describes semiconservative DNA replication?

Accepted Answer

Each new DNA molecule has half of the old one.

Question 14

In the lac operon, what is the role of the repressor protein?

Accepted Answer

It blocks transcription by binding the operator.

Question 15

Which of the following best explains why the lac operon is OFF when glucose is present, regardless of whether lactose is present?

Accepted Answer

Glucose lowers cAMP, so CAP cannot bind and transcription does not occur. This is called catabolite repression.

Question 16

A DNA sample contains 28% guanine nucleotides. What is the percentage of adenine nucleotides in this sample?

Accepted Answer

$22\%$

Question 17

Which of the following is a similarity between RNA and DNA?

Accepted Answer

Both have nucleotides consisting of a phosphate, sugar, and nitrogen base.

Question 18

During translation in prokaryotes, when does translation begin?

Accepted Answer

During transcription.

Question 19

Which of the following best describes the relationship among DNA, a gene, and a chromosome?

Accepted Answer

A chromosome contains hundreds of genes, which are composed of DNA.

Question 20

A scientist is studying the lac operon in E. coli. If both lactose and glucose are absent, which proteins will bind to the operon, and is the operon ON or OFF?

Accepted Answer

Repressor, CAP, and RNA polymerase; operon OFF

Microbiology Study Guide: DNA, RNA, and Gene Regulation

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