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

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

Question 1

Archibald Garrod described alkaptonuria as an 'inborn error of metabolism.' Which of the following best explains why this disease is not caused by an infectious agent?

Accepted Answer

It is caused by a defective enzyme in a biochemical pathway, not by bacteria or viruses.

Question 2

Which of the following best describes the relationship between genes and enzymes according to the 'one gene-one enzyme' hypothesis proposed by Beadle and Tatum?

Accepted Answer

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

Question 3

A mutation in the gene encoding phenylalanine hydroxylase (PAH) leads to phenylketonuria (PKU). What is the biochemical consequence of this mutation?

Accepted Answer

Phenylalanine accumulates because it cannot be converted to tyrosine.

Question 4

Which of the following amino acids is classified as hydrophobic and is most likely to be found in the interior of a protein?

Accepted Answer

Valine

Question 5

A protein's tertiary structure is primarily stabilized by which types of interactions?

Accepted Answer

Hydrogen bonds, ionic bonds, and hydrophobic interactions

Question 6

In the context of sickle cell anemia, which single amino acid change occurs in the beta hemoglobin protein?

Accepted Answer

Glutamic acid is replaced by valine at position 6

Question 7

Which of the following best describes the quaternary structure of hemoglobin?

Accepted Answer

It consists of four polypeptide subunits: two alpha and two beta chains.

Question 8

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

Accepted Answer

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

Question 9

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

Accepted Answer

$$	ext{Amino acid}_1 + 	ext{Amino acid}_2 ightarrow 	ext{Dipeptide} + 	ext{H}_2	ext{O}$$

Question 10

Which of the following best explains why sickle cell anemia persists at high frequencies in populations where malaria is common?

Accepted Answer

Heterozygotes for the sickle cell allele have increased resistance to malaria, leading to higher fitness.

Question 11

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes are proteins that catalyze specific chemical reactions by lowering the activation energy.

Question 12

A mutation in the gene encoding N-acetylhexosaminidase A (HEXA) leads to Tay-Sachs disease. What is the primary effect of this mutation?

Accepted Answer

Accumulation of substrate in neurons, causing neurodegeneration.

Question 13

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

Accepted Answer

The linear sequence of amino acids joined by covalent peptide bonds.

Question 14

In a biochemical pathway, what happens if an enzyme is missing due to a gene mutation?

Accepted Answer

The substrate for that enzyme accumulates, potentially causing disease.

Question 15

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

Accepted Answer

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

Question 16

Which of the following is a correct statement about the central dogma of molecular genetics?

Accepted Answer

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

Question 17

Which of the following best describes an auxotrophic strain of Neurospora?

Accepted Answer

It cannot grow on minimal media and requires an additional compound for growth.

Question 18

Which of the following amino acids is classified as acidic?

Accepted Answer

Glutamic acid

Question 19

Which of the following best explains the molecular basis of sickle cell anemia?

Accepted Answer

A single base pair change in the DNA sequence causes a single amino acid substitution in the beta hemoglobin protein.

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

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