Question 1

Which of the following best describes the molecular cause of alkaptonuria as discovered by Archibald Garrod?

Accepted Answer

A recessive mutation in a gene encoding an enzyme in the phenylalanine breakdown pathway, causing homogentisic acid to accumulate.

Question 2

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

Accepted Answer

$$\mathrm{Amino\ acid}_1 + \mathrm{Amino\ acid}_2 \rightarrow \mathrm{Dipeptide} + \mathrm{H}_2\mathrm{O}$$

Question 3

A mutation in the gene encoding phenylalanine hydroxylase (PAH) leads to which human disease, and what is the biochemical consequence?

Accepted Answer

Phenylketonuria (PKU); accumulation of phenylalanine

Question 4

Which of the following statements about protein structure is correct?

Accepted Answer

The tertiary structure is determined solely by the sequence of amino acids and their interactions.

Question 5

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

Accepted Answer

The sickle cell allele confers resistance to malaria in heterozygotes, increasing their fitness in malarial regions.

Question 6

Which of the following is the correct sequence of events in the central dogma of molecular biology?

Accepted Answer

$$\mathrm{DNA} \rightarrow \mathrm{RNA} \rightarrow \mathrm{Protein}$$

Question 7

A Neurospora mutant cannot grow on minimal medium but grows when methionine is added. What is the most likely explanation?

Accepted Answer

The mutant has a defect in a gene required for methionine synthesis.

Question 8

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 catalyzes a specific step in a biochemical pathway.

Question 9

Which of the following amino acids is classified as nonpolar based on its R group?

Accepted Answer

Valine

Question 10

A single base pair change in the DNA sequence of the beta hemoglobin gene results in which amino acid substitution in sickle cell anemia?

Accepted Answer

Glutamic acid to valine at position 6

Question 11

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 12

Which of the following diseases is caused by a defect in a lysosomal enzyme, leading to the accumulation of a molecule in neurons?

Accepted Answer

Tay-Sachs disease

Question 13

Which of the following best describes the role of the active site of an enzyme?

Accepted Answer

It is the region where the enzyme binds its substrate and catalyzes a chemical reaction.

Question 14

Which of the following is a real-world application of the auxotroph assay described in the study materials?

Accepted Answer

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

Question 15

Which of the following best explains why a mutation in a single gene can lead to a dramatic change in phenotype, as seen in sickle cell anemia?

Accepted Answer

A single amino acid change can alter the protein's 3D structure, affecting its function.

Question 16

Which of the following best describes a prototroph in the context of Neurospora genetics?

Accepted Answer

A strain that can synthesize all vitamins and amino acids needed for life from minimal medium.

Question 17

Which of the following is a direct consequence of a missing enzyme in a metabolic pathway?

Accepted Answer

The substrate for the missing enzyme accumulates.

Question 18

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

Accepted Answer

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

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

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