Question 1

Archibald Garrod's study of alkaptonuria led to the concept of 'inborn errors of metabolism.' Which of the following best describes the molecular basis of alkaptonuria?

Accepted Answer

A mutation in a gene encoding an enzyme required for the breakdown of homogentisic acid, leading to its accumulation.

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 covalent peptide bonds. $$	ext{Primary structure: } 	ext{Amino acid sequence}$$

Question 3

A patient is diagnosed with phenylketonuria (PKU). Which enzyme is deficient, and what is the consequence of this deficiency?

Accepted Answer

Phenylalanine hydroxylase is deficient, leading to the accumulation of phenylalanine and its toxic byproducts.

Question 4

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

Accepted Answer

They are hydrophilic and interact favorably with water molecules.

Question 5

Beadle and Tatum's experiments with Neurospora crassa led to which major genetic hypothesis?

Accepted Answer

One gene-one enzyme hypothesis

Question 6

A Neurospora mutant can grow on minimal medium supplemented with citrulline or arginine, but not with ornithine. Which enzyme is most likely defective in this mutant?

Accepted Answer

The enzyme that converts ornithine to citrulline

Question 7

Which of the following best describes the molecular change that causes sickle cell anemia?

Accepted Answer

A single base pair change in the DNA sequence leads to a glutamic acid to valine substitution at position 6 of the beta-globin chain. $$	ext{Glu} ightarrow 	ext{Val}$$

Question 8

Why do individuals who are heterozygous for the sickle cell allele (bAbS) have a selective advantage in regions where malaria is prevalent?

Accepted Answer

Their red blood cells have a shorter lifespan, disrupting the life cycle of Plasmodium falciparum.

Question 9

Which of the following is NOT a correct statement about enzymes?

Accepted Answer

All proteins are enzymes.

Question 10

A child is born with Tay-Sachs disease. Which of the following statements is true regarding the molecular basis of this disease?

Accepted Answer

It is caused by a deficiency of the lysosomal enzyme hexosaminidase A, leading to the accumulation of GM2 ganglioside in neurons.

Question 11

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

Accepted Answer

The association of multiple polypeptide chains to form a functional protein complex.

Question 12

Which of the following is a real-world example of a monogenic disease caused by a mutation in a gene encoding a non-enzyme protein?

Accepted Answer

Sickle cell anemia

Question 13

Which of the following best explains why a single amino acid substitution can drastically alter the function of a protein?

Accepted Answer

It can change the protein's 3D structure, affecting its ability to interact with other molecules or perform its function.

Question 14

Which of the following best describes the difference between a prototroph and an auxotroph in Neurospora crassa?

Accepted Answer

A prototroph can grow on minimal medium, while an auxotroph requires supplementation with a specific nutrient.

Question 15

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

Accepted Answer

$$	ext{Amino acid}_1 - \mathrm{COOH} + 	ext{Amino acid}_2 - \mathrm{NH}_2 ightarrow 	ext{Amino acid}_1 - \mathrm{CO}-\mathrm{NH}-	ext{Amino acid}_2 + \mathrm{H}_2\mathrm{O}$$

Question 16

A mutation in a gene encoding an enzyme in a metabolic pathway can lead to the accumulation of which of the following?

Accepted Answer

The substrate of the missing enzyme

Question 17

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

$$	ext{DNA} ightarrow 	ext{RNA} ightarrow 	ext{Protein}$$

Question 18

Which of the following is a correct statement about the relationship between genotype and phenotype?

Accepted Answer

Genotype refers to the genetic information (DNA), while phenotype refers to the observable traits resulting from gene expression.

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

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