Question 1

Which enzyme is responsible for synthesizing the leading strand during DNA replication, and in which direction does it synthesize the new strand?

Accepted Answer

DNA polymerase III; 5' to 3'

Question 2

During DNA replication, what is the role of primase?

Accepted Answer

It synthesizes short RNA primers to provide a starting point for DNA polymerase.

Question 3

Which of the following best describes the difference between the leading and lagging strands during DNA replication?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments.

Question 4

What is the error rate for DNA replication, and what mechanism helps maintain this low error rate?

Accepted Answer

1 error per billion nucleotides; proofreading by DNA polymerase

Question 5

Which base pairing is correct according to the rules of DNA base pairing?

Accepted Answer

Adenine pairs with thymine, guanine pairs with cytosine

Question 6

During transcription in eukaryotes, what is the function of the TATA box?

Accepted Answer

It is a promoter sequence that helps position RNA polymerase II for transcription initiation.

Question 7

Which of the following modifications occur to eukaryotic pre-mRNA before it becomes mature mRNA?

Accepted Answer

Addition of a 5' cap and a poly-A tail, and removal of introns

Question 8

What is the significance of alternative splicing in eukaryotic cells?

Accepted Answer

It allows a single gene to code for multiple proteins.

Question 9

Which of the following statements about transcription and translation in prokaryotes is correct?

Accepted Answer

Transcription and translation can occur simultaneously in the cytoplasm.

Question 10

A mutation changes a DNA sequence from 3'-TAC-5' to 3'-TAT-5'. What is the effect on the mRNA and the resulting protein?

Accepted Answer

The mRNA codon changes from 5'-AUG-3' to 5'-AUA-3', possibly changing the amino acid from methionine to isoleucine.

Question 11

Which enzyme is responsible for removing RNA primers and replacing them with DNA nucleotides during DNA replication?

Accepted Answer

DNA polymerase I

Question 12

What is the function of the spliceosome in eukaryotic cells?

Accepted Answer

It removes introns from pre-mRNA and joins exons together.

Question 13

Which of the following best explains why the error rate for translation is higher than for DNA replication?

Accepted Answer

Translation does not involve proofreading mechanisms like DNA replication does.

Question 14

What is the role of aminoacyl-tRNA synthetase in translation?

Accepted Answer

It matches each tRNA with its correct amino acid.

Question 15

Which of the following is a direct result of the 'wobble' hypothesis in tRNA anticodon-codon pairing?

Accepted Answer

A single tRNA can recognize multiple codons for the same amino acid.

Question 16

Which of the following best describes the process of translation elongation?

Accepted Answer

Amino acids are added one by one to the growing polypeptide chain as tRNAs bring them to the ribosome.

Question 17

What is the main function of the 5' cap and poly-A tail added to eukaryotic mRNA?

Accepted Answer

They facilitate mRNA export from the nucleus, protect mRNA from degradation, and help ribosomes bind to the mRNA.

Question 18

Which of the following statements about polyribosomes is correct?

Accepted Answer

They allow a single mRNA molecule to be translated by multiple ribosomes simultaneously, increasing protein production.

Question 19

A scientist observes that a mutation in the polyadenylation signal (AAUAAA) of a gene leads to unstable mRNA. What is the most likely explanation?

Accepted Answer

The mRNA lacks a poly-A tail, making it more susceptible to degradation.

Transcription and Translation: Gene Expression

Study Guide - Practice Questions