Question 1

Which of the following best describes the 'one gene, one polypeptide' hypothesis as it is understood today?

Accepted Answer

Each gene encodes a single polypeptide, which may function alone or as part of a protein complex.

Question 2

A patient is diagnosed with alkaptonuria, a disorder in which homogentisic acid accumulates. Based on the metabolic pathway for phenylalanine and tyrosine breakdown, which enzyme is most likely nonfunctional in this patient?

Accepted Answer

Homogentisic acid oxidase

Question 3

In the Beadle and Tatum experiment with Neurospora crassa, a mutant strain could grow on minimal medium supplemented with citrulline or arginine, but not with ornithine. Which enzyme is most likely defective in this strain?

Accepted Answer

Enzyme 2 (converts ornithine to citrulline)

Question 4

Which of the following statements about the central dogma of molecular biology is correct?

Accepted Answer

Information flows from DNA to RNA to protein.

Question 5

During transcription in bacteria, what is the role of the sigma factor?

Accepted Answer

It recognizes the promoter region and helps RNA polymerase bind to DNA.

Question 6

Which of the following modifications occurs to eukaryotic pre-mRNA before it becomes mature mRNA?

Accepted Answer

Addition of a 5' methylguanosine cap and a 3' poly A tail

Question 7

A tRNA has the anticodon sequence 3'–CAG–5'. Which mRNA codon will it recognize, and which amino acid will it carry?

Accepted Answer

5'–GUC–3'; valine

Question 8

Which of the following best explains why the genetic code is described as 'redundant'?

Accepted Answer

Multiple codons can specify the same amino acid.

Question 9

What would be the most likely consequence of a frameshift mutation caused by the insertion of a single nucleotide near the start of a coding sequence?

Accepted Answer

All codons downstream of the mutation would be altered, likely resulting in a nonfunctional protein.

Question 10

Which of the following statements about ribosomes is correct?

Accepted Answer

Ribosomes are composed of rRNA and protein and have distinct sites for tRNA binding and polypeptide synthesis.

Question 11

Which of the following is a function of the spliceosome in eukaryotic cells?

Accepted Answer

It removes introns from pre-mRNA and joins exons together.

Question 12

A mutation in the gene encoding aminoacyl-tRNA synthetase results in the enzyme attaching the wrong amino acid to a tRNA. What is the most likely consequence for the cell?

Accepted Answer

The wrong amino acid will be incorporated into the growing polypeptide, potentially altering protein function.

Question 13

Which of the following best describes the role of the promoter in transcription?

Accepted Answer

It is the site where RNA polymerase binds to initiate transcription.

Question 14

During translation elongation, what is the function of the peptidyl transferase activity of the ribosome?

Accepted Answer

It forms peptide bonds between amino acids in the growing polypeptide chain.

Question 15

Which of the following is NOT a property of the genetic code?

Accepted Answer

It is ambiguous.

Question 16

A scientist synthesizes an mRNA composed entirely of repeating UUU codons. Which polypeptide will be produced during translation?

Accepted Answer

A polypeptide composed entirely of phenylalanine residues

Question 17

Which of the following best explains why antibiotics that target bacterial ribosomes do not affect eukaryotic ribosomes?

Accepted Answer

Bacterial and eukaryotic ribosomes have structural differences that antibiotics can exploit.

Question 18

Which of the following is a direct result of alternative splicing in eukaryotic cells?

Accepted Answer

A single gene can produce multiple protein isoforms.

Question 19

Which of the following statements about the directionality of transcription and translation is correct?

Accepted Answer

Transcription synthesizes RNA in the 5' to 3' direction, and translation reads mRNA from 5' to 3'.

Chapter 12

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