Question 1

Which of the following statements best describes the semiconservative model of DNA replication?

Accepted Answer

Each daughter DNA molecule consists of one parental strand and one newly synthesized strand.

Question 2

During eukaryotic DNA replication, what is the significance of multiple fixed origins of replication?

Accepted Answer

They enable bidirectional replication from several points, increasing efficiency.

Question 3

Which enzyme is responsible for relieving the torsional stress generated during DNA unwinding by helicase?

Accepted Answer

Topoisomerase

Question 4

What is the chemical reaction catalyzed by DNA polymerase during chain elongation?

Accepted Answer

Nucleophilic attack by the 3'-OH of the primer on the $\alpha$-phosphate of the incoming dNTP, forming a phosphodiester bond

Question 5

Which activities are associated with DNA polymerase I in E. coli?

Accepted Answer

Polymerase, 3'-exonuclease, and 5'-exonuclease activities

Question 6

In the discontinuous synthesis of the lagging strand, what are the short DNA fragments called?

Accepted Answer

Okazaki fragments

Question 7

Which enzyme synthesizes the RNA primers required for DNA replication?

Accepted Answer

Primase

Question 8

What is the role of small nuclear ribonucleoproteins (snRNPs) in posttranscriptional processing?

Accepted Answer

They aid in the splicing of pre-mRNA by forming the spliceosome.

Question 9

Which modification at the 5'-end of eukaryotic pre-mRNA increases its stability and is essential for translation?

Accepted Answer

Capping with 7-methylguanosine

Question 10

Alternative splicing allows a single gene to:

Accepted Answer

Specify multiple proteins by generating different mRNA isoforms

Question 11

Which of the following is true regarding the genetic code?

Accepted Answer

The AUG codon encodes methionine and serves as the start codon in eukaryotes.

Question 12

During translation, the anticodon loop of tRNA pairs with:

Accepted Answer

The complementary trinucleotide codon in mRNA

Question 13

What is the correct order of the three sites in the ribosome that interact with tRNA during translation?

Accepted Answer

A (aminoacyl), P (peptidyl), E (exit)

Question 14

Which process is directly associated with increased transcriptional activity in eukaryotic cells?

Accepted Answer

Acetylation of core histones

Question 15

What is the function of the TATA box in eukaryotic promoters?

Accepted Answer

It serves as the binding site for transcription factors and helps initiate transcription.

Question 16

Which of the following statements about DNA methylation in eukaryotes is correct?

Accepted Answer

DNA methylation can lead to permanent gene inactivation and is involved in X chromosome inactivation and imprinting.

Question 17

Which enzyme is responsible for adding the poly(A) tail to eukaryotic mRNA during transcription termination?

Accepted Answer

Poly(A) polymerase

Question 18

What is the effect of acetylation of lysine residues in histones on chromatin structure?

Accepted Answer

It neutralizes the basic lysine residues, weakening histone-DNA interactions and promoting transcription.

Question 19

Which of the following best describes the process of nick translation during DNA replication?

Accepted Answer

DNA polymerase I removes RNA primers and replaces them with deoxynucleotides using its exonuclease and polymerase activities.

Question 20

Which step in protein synthesis involves the activation of amino acids by ATP and their attachment to tRNA?

Accepted Answer

Formation of aminoacyl-tRNA by aminoacyl-tRNA synthetase

DNA Replication, Transcription, and Translation: Key Concepts in Molecular Biology

Study Guide - Practice Questions