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 degradation pathway, leading to accumulation of homogentisic acid.

Question 2

Which experimental approach did Beadle and Tatum use to demonstrate the 'one gene, one enzyme' hypothesis?

Accepted Answer

They used X-rays to induce mutations in Neurospora and identified mutants that could not grow on minimal medium.

Question 3

Which of the following statements about protein structure is CORRECT?

Accepted Answer

The quaternary structure involves the assembly of multiple polypeptide chains into a functional protein complex.

Question 4

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 converting ornithine to citrulline.

Question 5

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

Accepted Answer

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

Question 6

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 7

Which amino acid substitution is responsible for sickle cell anemia?

Accepted Answer

Glutamic acid (E) is replaced by valine (V) at position 6 of the beta hemoglobin chain.

Question 8

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

Accepted Answer

A strain that requires an additional nutrient because it cannot synthesize it due to a gene mutation.

Question 9

Which of the following is a direct consequence of a single base pair change in the DNA sequence of a gene?

Accepted Answer

A change in the amino acid sequence of the encoded protein, potentially altering its structure and function.

Question 10

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

Accepted Answer

Enzymes act as catalysts, speeding up specific chemical reactions at each step of a pathway.

Question 11

A child is diagnosed with phenylketonuria (PKU). Which enzyme is defective, and what is the consequence?

Accepted Answer

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

Question 12

Which of the following best explains why charged and polar amino acids are generally found on the outside of proteins?

Accepted Answer

They are hydrophilic and interact favorably with the aqueous environment.

Question 13

Which of the following is NOT a correct statement about the central dogma of molecular biology?

Accepted Answer

Proteins store genetic information for inheritance.

Question 14

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

Accepted Answer

Tay-Sachs disease

Question 15

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

Accepted Answer

Genotype determines the sequence of DNA, which is transcribed and translated to produce proteins that determine phenotype.

Question 16

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

Accepted Answer

It can change the protein's three-dimensional structure, affecting its ability to interact with other molecules.

Question 17

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

Accepted Answer

Screening newborns for metabolic diseases caused by enzyme deficiencies.

Question 18

Which of the following best describes a peptide bond?

Accepted Answer

A covalent bond between the carboxyl group of one amino acid and the amino group of the next.

Question 19

Which of the following is a consequence of the sickle cell mutation at the population level in regions with malaria?

Accepted Answer

Heterozygotes have a selective advantage, leading to maintenance of the sickle cell allele in the population.

Genes, Proteins, and Human Disease: The Molecular Basis of Heredity and Variation

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