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

Question 1

Which experiment led to the formulation of the one-gene, one-enzyme hypothesis, and what was the main finding?

Accepted Answer

Beadle and Tatum irradiated bread mold and found that each mutant was defective in a single enzyme required for a metabolic pathway.

Question 2

What is the central dogma of molecular biology?

Accepted Answer

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

Question 3

Which of the following best describes the role of mRNA in gene expression?

Accepted Answer

It carries genetic information from DNA in the nucleus to the site of protein synthesis in the cytoplasm.

Question 4

A mutation changes a codon from UAU (tyrosine) to UAA. What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 5

Which property of the genetic code allows multiple codons to specify the same amino acid?

Accepted Answer

Redundancy

Question 6

A patient’s karyotype reveals a chromosome with a segment that has broken off, flipped, and rejoined. What type of mutation is this?

Accepted Answer

Inversion

Question 7

If a DNA sequence is mutated from CCT to CCA, and both code for proline, what type of mutation has occurred?

Accepted Answer

Silent mutation

Question 8

Which enzyme is responsible for synthesizing RNA from a DNA template during transcription?

Accepted Answer

RNA polymerase

Question 9

A mutation that shifts the reading frame of the genetic message by inserting or deleting a nucleotide is called:

Accepted Answer

Frameshift mutation

Question 10

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

Accepted Answer

Each codon codes for more than one amino acid.

Question 11

A scientist observes that a mutation in a gene does not change the phenotype of an organism. Which explanation is most likely?

Accepted Answer

The mutation is neutral and does not affect protein function.

Question 12

Which codon serves as the start signal for translation in most organisms?

Accepted Answer

$$AUG$$

Question 13

A segment of DNA is transcribed into the mRNA sequence 5'-AUGGCCUAA-3'. What is the corresponding amino acid sequence?

Accepted Answer

Methionine-Alanine-Stop

Question 14

Which of the following best explains why a frameshift mutation is often more damaging than a point mutation?

Accepted Answer

It alters the reading frame, changing all downstream amino acids.

Question 15

Reverse transcriptase is an enzyme found in some viruses. What is its function?

Accepted Answer

It synthesizes DNA from an RNA template.

Question 16

Which of the following is an example of a chromosome-level mutation?

Accepted Answer

Translocation

Question 17

A mutation changes the DNA sequence from AAA (lysine) to GAA (glutamic acid). What type of mutation is this?

Accepted Answer

Missense mutation

Question 18

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

Accepted Answer

Genotype determines the sequence of proteins, which in turn determines phenotype.

Question 19

Which of the following is NOT a property of the genetic code?

Accepted Answer

Overlapping

Question 20

A cancer cell is found to have an extra copy of chromosome 21. What type of mutation is this?

Accepted Answer

Aneuploidy

How Genes Work: The Molecular Basis of Gene Expression and Mutation

Study Guide - Practice Questions