$$\text{Amino acid}_1 + \text{Amino acid}_2 \rightarrow \text{Dipeptide} + H_2O$$

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

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 the accumulation of homogentisic acid.

Question 2

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

Accepted Answer

$$	ext{Amino acid}_1 + 	ext{Amino acid}_2 ightarrow 	ext{Dipeptide} + H_2O$$

Question 3

Which level of protein structure is primarily determined by the sequence of amino acids?

Accepted Answer

Primary structure

Question 4

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

Accepted Answer

Phenylketonuria (PKU)

Question 5

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.

Question 6

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

Accepted Answer

One gene-one enzyme hypothesis

Question 7

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

Accepted Answer

The enzyme that converts ornithine to citrulline

Question 8

Which of the following statements about sickle cell anemia is correct?

Accepted Answer

It is caused by a single amino acid substitution (E6V) in the beta hemoglobin chain.

Question 9

Why do individuals heterozygous for the sickle cell allele (bAbS) have a selective advantage in malaria-endemic regions?

Accepted Answer

Their red blood cells are less hospitable to Plasmodium falciparum, disrupting the parasite's life cycle.

Question 10

Which of the following best describes an auxotrophic mutant in Neurospora?

Accepted Answer

A strain that cannot grow on minimal medium unless a specific nutrient is added.

Question 11

Which of the following equations best represents the central dogma of molecular biology?

Accepted Answer

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

Question 12

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

Accepted Answer

Storing genetic information

Question 13

A child is diagnosed with Tay-Sachs disease. Which of the following best explains the molecular basis of this disease?

Accepted Answer

A mutation in the HEXA gene leads to accumulation of a substrate in neurons, causing neurodegeneration.

Question 14

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.

Question 15

Which of the following best explains why a single base pair change in DNA can cause a severe genetic disease?

Accepted Answer

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

Question 16

Which of the following is a real-world application of the one gene-one enzyme hypothesis?

Accepted Answer

Screening newborns for PKU to prevent mental retardation by dietary intervention.

Question 17

Which of the following amino acids is classified as nonpolar?

Accepted Answer

Valine

Question 18

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

Accepted Answer

They catalyze specific steps, and a defect in one enzyme can block the entire pathway.

Question 19

A patient’s urine turns black upon standing. Which metabolic defect is most likely present?

Accepted Answer

A defect in the enzyme that breaks down homogentisic acid, leading to alkaptonuria.

Question 20

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

Accepted Answer

Heterozygotes for the sickle cell allele have increased resistance to malaria, maintaining the allele in the population.

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

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