DNA replication

Which of the following is a key difference between leading and lagging strand synthesis during DNA replication?

• Leading strand is synthesized in fragments, lagging strand continuously.

• Leading strand requires RNA primers, lagging strand does not.

• Leading strand is synthesized continuously, lagging strand in Okazaki fragments.

• Both are synthesized discontinuously.

Which enzyme is responsible for unwinding the DNA double helix during replication?

• DNA polymerase

• Primase

• Helicase

• Exonuclease

What role does the enzyme primase play in DNA replication?

• Synthesizes DNA strands

• Synthesizes RNA primers

• Joins Okazaki fragments

• Repairs mismatched nucleotides

Which of the following enzymes relieves the tension created ahead of the replication fork during DNA replication?

• DNA polymerase

• Helicase

• Topoisomerase

• DNA ligase

How does cisplatin inhibit DNA replication in cancer cells?

• Inhibits DNA polymerase directly

• Causes the formation of interstrand and intrastrand cross-links in DNA

• Prevents helicase from unwinding DNA

• Inhibits topoisomerase I activity

What is the primary mechanism of action of topoisomerase inhibitors in cancer therapy?

• Prevents the initiation of DNA replication by inhibiting helicase

• Inhibits DNA polymerase, halting DNA strand elongation

• Stabilizes the DNA-topoisomerase complex, leading to double-strand DNA breaks

• Prevents DNA strand separation by inhibiting primase activity

What type of mutation occurs when a single nucleotide substitution results in the premature formation of a stop codon?

• Missense mutation

• Nonsense mutation

• Silent mutation

• Frameshift mutation

What type of DNA damage does the nucleotide excision repair (NER) pathway primarily correct?

• Double-strand breaks

• Single-strand breaks

• Helix-distorting lesions such as thymine dimers caused by UV light

• Oxidative base damage

Which enzyme is responsible for the first step in the base excision repair (BER) pathway?

• DNA ligase

• DNA polymerase

• Glycosylase

• Exonuclease

Which enzyme seals the final "nick" in the DNA backbone after the repair process is complete?

• DNA ligase

• DNA polymerase

• Exonuclease

• Helicase