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 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.

Question 3

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

Accepted Answer

Phenylalanine hydroxylase is defective, causing phenylalanine to accumulate and be converted into harmful products.

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 molecules.

Question 5

Beadle and Tatum’s experiments with Neurospora crassa led to which important genetic hypothesis?

Accepted Answer

One gene makes one enzyme.

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?

Accepted Answer

The enzyme that converts ornithine to citrulline.

Question 7

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

Accepted Answer

A single base pair change in the DNA leads to a glutamic acid being replaced by valine at the 6th position of the beta hemoglobin chain.

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 half-life, disrupting the life cycle of Plasmodium falciparum.

Question 9

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

Accepted Answer

All enzymes are made of nucleic acids.

Question 10

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

Accepted Answer

It is caused by a mutation in the gene encoding the lysosomal enzyme N-acetylhexosaminidase A (HEXA).

Question 11

Which of the following best describes the relationship between genotype and phenotype as explained by the central dogma of molecular biology?

Accepted Answer

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

Question 12

Which of the following is a correct statement about the quaternary structure of proteins?

Accepted Answer

It involves the association of multiple polypeptide chains to form a functional protein complex.

Question 13

Which of the following best explains why a single amino acid substitution (such as E6V in hemoglobin) can have drastic effects on protein function?

Accepted Answer

It can alter the three-dimensional structure of the protein, affecting its ability to function properly.

Question 14

A mutation in a gene leads to the accumulation of a substrate in a metabolic pathway. Which of the following is the most likely explanation?

Accepted Answer

The enzyme that acts on that substrate is nonfunctional due to the mutation.

Question 15

Which of the following best describes a prototrophic strain of Neurospora?

Accepted Answer

It can grow on minimal media because it can synthesize all required vitamins and amino acids.

Question 16

Which of the following is a real-world application of the knowledge that mutations in single genes can cause metabolic diseases?

Accepted Answer

Newborn screening for PKU to prevent mental retardation by dietary intervention.

Question 17

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

Accepted Answer

Valine

Question 18

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

Accepted Answer

It is the region where the substrate binds and the chemical reaction occurs.

Question 19

Which of the following is a correct statement about the inheritance pattern of alkaptonuria as described by Garrod?

Accepted Answer

It is a recessive Mendelian trait.

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

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