Which enzyme primarily is responsible for joining 'Okazaki fragments' during the DNA replication process?
Show answer & explanation
Correct answer: B
Explanation
Answer: DNA Ligase.
Explanation:
- During DNA replication, the synthesis of DNA on the 'lagging strand' occurs in small fragments known as Okazaki fragments. The crucial task of joining these fragments together is performed by the enzyme DNA ligase. This enzyme fills the 'nicks' or gaps between adjacent DNA segments by forming phosphodiester bonds, thereby creating a continuous DNA strand. It is often referred to as 'molecular glue.'
- Description of Other Options:
- DNA Polymerase: This is the primary enzyme responsible for synthesizing new DNA strands by adding new nucleotides.
- Helicase: This enzyme unwinds or separates the DNA double helix, thereby creating a replication fork.
- Primase: This enzyme synthesizes RNA primers, which provide a starting point for DNA polymerase to begin its work.
Additional Points:
- Key Fact: Okazaki fragments are named after the Japanese scientists Reiji Okazaki and Tsuneko Okazaki, who discovered them in the 1960s.
- Directionality: DNA synthesis always proceeds in the 5' to 3' direction.
Potential Exam Questions and Answers:
Question: Which enzyme is responsible for unwinding the DNA double helix?
Answer: Helicase.
Question: On which strand of DNA are Okazaki fragments formed?
Answer: On the lagging strand.
Question: Which enzyme is known as 'molecular scissors'?
Answer: Restriction Endonuclease.