Question 1

Which of the following statements best explains why RNA can serve as a bridge between DNA and protein synthesis?

Accepted Answer

RNA is single-stranded and can leave the nucleus, carrying genetic information to ribosomes for translation.

Question 2

A scientist observes that in bacteria, translation of mRNA can begin before transcription has finished. Which cellular feature allows this process?

Accepted Answer

Absence of a nucleus, allowing ribosomes access to mRNA as it is being transcribed.

Question 3

Which codon acts as the initiation signal for translation, and what amino acid does it code for?

Accepted Answer

AUG; codes for methionine.

Question 4

During transcription, RNA polymerase catalyzes the addition of RNA nucleotides to the DNA template strand. In which direction does RNA synthesis occur?

Accepted Answer

RNA is synthesized in the $$5' \rightarrow 3'$$ direction.

Question 5

Which of the following best describes the function of the polyadenylation signal sequence (AAUAAA) in eukaryotic transcription?

Accepted Answer

It signals the termination of transcription and initiates RNA processing.

Question 6

A mutation causes the removal of the 5’ cap from an mRNA molecule in a eukaryotic cell. Which of the following consequences is most likely?

Accepted Answer

The mRNA will be unable to exit the nucleus and will be degraded.

Question 7

Which process removes introns and joins exons in a eukaryotic pre-mRNA molecule?

Accepted Answer

RNA splicing

Question 8

A charged tRNA molecule is defined as:

Accepted Answer

A tRNA that is bound to its specific amino acid.

Question 9

During translation, which ribosomal site holds the tRNA carrying the growing polypeptide chain?

Accepted Answer

P site

Question 10

Which of the following best describes the role of GTP in translation?

Accepted Answer

GTP provides energy for the movement of ribosomes and tRNA during translation.

Question 11

A mutation changes a codon from UAU (tyrosine) to UAA. What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; introduces a premature stop codon, likely resulting in a nonfunctional protein.

Question 12

A frameshift mutation is most likely caused by:

Accepted Answer

Insertion or deletion of nucleotides that alters the reading frame.

Question 13

Which of the following best explains why silent mutations do not affect the amino acid sequence of a protein?

Accepted Answer

The genetic code is redundant, so multiple codons can code for the same amino acid.

Question 14

A polyribosome (polysome) is best described as:

Accepted Answer

A group of ribosomes simultaneously translating the same mRNA molecule.

Question 15

Which of the following is a real-life example of a point mutation that can be transmitted to offspring?

Accepted Answer

Sickle-cell disease caused by a single nucleotide substitution.

Question 16

Which of the following steps occurs first during the initiation of translation in eukaryotes?

Accepted Answer

The small ribosomal subunit binds to the mRNA and scans for the start codon.

Question 17

A protein is found to be nonfunctional because it lacks a phosphate group that is normally added after translation. This is an example of:

Accepted Answer

A failure in post-translational modification.

Question 18

Which of the following best describes the relationship between codons and anticodons during translation?

Accepted Answer

Codons are found on mRNA and anticodons are found on tRNA, allowing base pairing for amino acid addition.

Question 19

A scientist wants to measure the rate of transcription in eukaryotic cells. If RNA polymerase adds nucleotides at a rate of 40 nucleotides per second, how many nucleotides will be added in 2 minutes?

Accepted Answer

$$40 	imes 120 = 4800$$ nucleotides

Question 20

A mutation in a gene results in the insertion of two nucleotides. What is the most likely outcome for the protein product?

Accepted Answer

The protein will have a frameshift mutation, likely resulting in a nonfunctional protein.

Gene Expression: From Gene to Protein – Transcription, Translation, and Mutations

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