Given four enzymes:
1. DNA polymerase
2. Ligase
3. Helicase
4. Peptidase.
Which are directly involved in DNA replication?
Show answer & explanation
Correct answer: C
Explanation
Answer: Options 1, 2, and 3.
Explanation:
- DNA replication is a process in which two identical copies are produced from a single DNA molecule. The following enzymes play a key role in this process:
- •Helicase: This is often referred to as the 'unzipping' enzyme. It separates the two strands of DNA by breaking the hydrogen bonds between them.
- •DNA Polymerase: This is the 'builder' enzyme. It adds new nucleotides based on the template strand and constructs the new strand.
- •Ligase: This is known as the 'glue' enzyme. It joins small fragments of DNA (such as Okazaki fragments) together to form a continuous strand.
- Peptidase is not part of this process, as its function is the digestion of proteins (breaking the peptide bonds between amino acids).
Additional Points:
- Primase: This is another important enzyme that synthesizes a 'primer,' which signals DNA polymerase to begin its work.
- Topoisomerase: This relieves the tension that arises as the DNA strands unwind.
- Direction of Replication: DNA synthesis always proceeds in the 5' to 3' direction.
Potential Questions and Answers:
Question: What is the term for the segments of DNA that are not synthesized continuously?
Answer: Okazaki fragments, which are subsequently joined together by ligase.
Question: In which phase of the cell cycle does DNA replication occur?
Answer: It occurs during the S-phase of Interphase.