Question 1

Which of the following best describes the main conclusion of Beadle and Tatum’s experiments with Neurospora crassa?

Accepted Answer

Each gene encodes a single enzyme that affects a single step in a metabolic pathway.

Question 2

A patient with alkaptonuria accumulates homogentisic acid in their urine. According to Garrod’s hypothesis, what is the most likely genetic cause?

Accepted Answer

A mutation in the gene encoding homogentisic acid oxidase.

Question 3

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

Accepted Answer

It is overlapping, so each nucleotide is part of multiple codons.

Question 4

Which codon serves as the start codon for translation in both prokaryotes and eukaryotes?

Accepted Answer

$$\mathrm{AUG}$$

Question 5

A mutation causes a frameshift in a gene. Which experimental result would best support the triplet nature of the genetic code?

Accepted Answer

A second, nearby insertion mutation restores the reading frame and protein function.

Question 6

Which of the following is TRUE regarding the difference between a polypeptide and a protein?

Accepted Answer

A protein is a polypeptide that folds into a stable three-dimensional structure.

Question 7

Which of the following best explains why sickle-cell anemia is considered a molecular disease?

Accepted Answer

It is caused by a single amino acid substitution in the β-globin polypeptide.

Question 8

Which of the following statements about tRNA is CORRECT?

Accepted Answer

Each tRNA has a specific anticodon that pairs with a codon in mRNA.

Question 9

What is the role of aminoacyl-tRNA synthetase in translation?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA.

Question 10

Which of the following best describes the directionality of polypeptide synthesis?

Accepted Answer

Amino acids are added to the C-terminal end of the growing polypeptide.

Question 11

In prokaryotes, what sequence helps the ribosome identify the start codon on mRNA?

Accepted Answer

Shine-Dalgarno sequence

Question 12

Which of the following is a property of the genetic code that allows multiple codons to specify the same amino acid?

Accepted Answer

Degeneracy

Question 13

Which of the following amino acids is encoded by the codon $$\mathrm{AUG}$$?

Accepted Answer

Methionine

Question 14

Which of the following statements about protein sorting in eukaryotic cells is TRUE?

Accepted Answer

Proteins destined for mitochondria have an N-terminal transit sequence that is removed after import.

Question 15

Which of the following is a stop codon in the standard genetic code?

Accepted Answer

$$\mathrm{UAG}$$

Question 16

A mutation in the gene encoding cystathionine γ-synthase in Neurospora crassa would most likely result in which phenotype?

Accepted Answer

The mutant would require cystathionine or a downstream supplement to grow on minimal medium.

Question 17

Which of the following best explains why the one gene–one enzyme hypothesis was modified to the one gene–one polypeptide hypothesis?

Accepted Answer

Some proteins are composed of multiple polypeptides, each encoded by a different gene.

Question 18

Which of the following is a real-world example of an inborn error of metabolism described by Garrod?

Accepted Answer

Alkaptonuria

Question 19

Which of the following statements about the wobble hypothesis is CORRECT?

Accepted Answer

The third base of the codon can form non-standard base pairs with the tRNA anticodon.

Ch 13 Translation of mRNA and the Genetic Basis of Protein Synthesis

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