Question 1

Which experiment by Beadle and Tatum provided evidence for the one gene–one enzyme hypothesis?

Accepted Answer

Exposing Neurospora cells to X-rays and screening for nutritional mutants that could not grow on minimal medium but could grow on complete medium.

Question 2

In the arginine biosynthetic pathway, a mutation in Gene B would result in the inability to synthesize which compound?

Accepted Answer

Citrulline

Question 3

What is the central dogma of molecular biology as described by Francis Crick?

Accepted Answer

DNA \rightarrow RNA \rightarrow Protein

Question 4

Why can translation begin before transcription is finished in bacterial cells?

Accepted Answer

Bacterial cells lack a nucleus, so mRNA is immediately accessible to ribosomes.

Question 5

A mutation in the gene encoding tyrosinase results in albinism. What is the direct consequence of this mutation?

Accepted Answer

The enzyme tyrosinase is nonfunctional, preventing melanin synthesis.

Question 6

Which of the following best describes the relationship between genotype and phenotype?

Accepted Answer

Proteins are the link between genotype and phenotype.

Question 7

If a Neurospora mutant can grow only when arginine is added to the minimal medium, which enzyme is most likely defective?

Accepted Answer

Enzyme C (converts citrulline to arginine)

Question 8

Which of the following statements about the genetic code is correct?

Accepted Answer

The genetic code is redundant but not ambiguous.

Question 9

During transcription, which strand of DNA is used to synthesize RNA?

Accepted Answer

The template strand

Question 10

What is the role of messenger RNA (mRNA) in gene expression?

Accepted Answer

It carries genetic information from DNA to the protein-synthesizing machinery.

Question 11

Which process involves the conversion of the nucleotide sequence of mRNA into the amino acid sequence of a polypeptide?

Accepted Answer

Translation

Question 12

A segment of DNA has the sequence 5'-ATGCGT-3'. What is the sequence of the corresponding mRNA transcript?

Accepted Answer

$$5'	ext{AUGCGU}\ 3'$$

Question 13

Which of the following best explains why the genetic code is nearly universal among all living organisms?

Accepted Answer

It evolved early in the history of life and is shared by all present-day organisms.

Question 14

If a mutation changes the reading frame of an mRNA, what is the most likely outcome?

Accepted Answer

The resulting polypeptide will be incorrect due to a frameshift mutation.

Question 15

Which of the following is a real-world application of the universality of the genetic code?

Accepted Answer

Bacteria can be engineered to produce human proteins such as insulin.

Question 16

In eukaryotic cells, what is the sequence of events for gene expression?

Accepted Answer

Transcription \rightarrow RNA processing \rightarrow Translation

Question 17

Which of the following is NOT a revision to the original one gene–one enzyme hypothesis?

Accepted Answer

Each gene codes for a single enzyme only.

Question 18

What is the significance of codon redundancy in the genetic code?

Accepted Answer

It allows multiple codons to specify the same amino acid, reducing the impact of mutations.

Question 19

Which of the following best describes the flow of genetic information in a eukaryotic cell?

Accepted Answer

DNA \rightarrow pre-mRNA \rightarrow mRNA \rightarrow Protein

Question 20

A Neurospora mutant grows on minimal medium plus citrulline but not on minimal medium plus ornithine. Which gene is most likely mutated?

Accepted Answer

Gene B (encoding enzyme B)

Gene Expression: From Gene to Protein – Transcription, Translation, and the Genetic Code

Study Guide - Practice Questions