Question 1

Which of the following best describes the molecular cause of alkaptonuria, as first described by Archibald Garrod?

Accepted Answer

A mutation in a gene encoding an enzyme in the phenylalanine breakdown pathway, leading to accumulation of homogentisic acid.

Question 2

Which of the following statements about the structure of proteins is CORRECT?

Accepted Answer

The primary structure of a protein is the linear sequence of amino acids joined by peptide bonds.

Question 3

A mutation in the gene encoding phenylalanine hydroxylase (PAH) leads to which human disease?

Accepted Answer

Phenylketonuria (PKU)

Question 4

Which of the following best explains why charged and polar amino acids are generally found on the outside of proteins in aqueous environments?

Accepted Answer

They are hydrophilic and interact favorably with water.

Question 5

In the context of Beadle and Tatum's experiments with Neurospora, what is an auxotroph?

Accepted Answer

A mutant strain that cannot synthesize a specific compound and requires it to be supplied in the medium.

Question 6

Which of the following equations correctly represents the formation of a peptide bond between two amino acids?

Accepted Answer

$$\mathrm{Amino\ acid\ 1\ +\ Amino\ acid\ 2 \rightarrow Dipeptide\ +\ H_2O}$$

Question 7

A child is diagnosed with Tay-Sachs disease. Which of the following best describes the molecular defect?

Accepted Answer

A mutation in the HEXA gene, leading to defective lysosomal enzyme and accumulation of substrate in neurons.

Question 8

Which of the following best explains why sickle cell anemia persists at high frequency in certain populations?

Accepted Answer

Heterozygotes for the sickle cell allele have increased resistance to malaria.

Question 9

Which of the following best describes the 'one gene, one enzyme' hypothesis proposed by Beadle and Tatum?

Accepted Answer

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

Question 10

A mutation changes the sixth amino acid in the beta chain of hemoglobin from glutamic acid (Glu) to valine (Val). Which of the following is the most likely consequence?

Accepted Answer

The hemoglobin protein changes shape, causing red blood cells to sickle under low oxygen conditions.

Question 11

Which of the following best describes the relationship between genotype and phenotype as explained by the Central Dogma?

Accepted Answer

DNA is transcribed to RNA, which is translated to protein, and the protein determines phenotype.

Question 12

Which of the following is a real-world application of the auxotroph assay described in the Neurospora experiments?

Accepted Answer

Screening newborns for phenylketonuria (PKU) by testing their ability to metabolize phenylalanine.

Question 13

Which of the following best explains why a single base pair change in DNA can lead to a drastic change in protein function?

Accepted Answer

It can change a single amino acid in the protein, altering its structure and function.

Question 14

Which of the following best describes the role of enzymes in biochemical pathways?

Accepted Answer

Each enzyme catalyzes a specific step, and a defect in one enzyme can block the entire pathway.

Question 15

Which of the following is a consequence of a mutation that inactivates the enzyme converting ornithine to citrulline in the arginine biosynthesis pathway?

Accepted Answer

The organism cannot grow unless citrulline or arginine is supplied in the medium.

Question 16

Which of the following best explains why the sickle cell allele is more common in populations from regions where malaria is endemic?

Accepted Answer

Heterozygotes have a selective advantage due to increased resistance to malaria.

Question 17

Which of the following is NOT a function of proteins in the cell?

Accepted Answer

Storing genetic information.

Question 18

Which of the following best describes the quaternary structure of a protein?

Accepted Answer

The arrangement of multiple polypeptide subunits in a functional protein complex.

Genes, Proteins, Enzymes, and Human Disease: Molecular Genetics Study Guide

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