Question
- Why does DNA replication occur in small replication forks and not in its entire length?
- Why is DNA replication continuous and discontinuous in a replication fork?
- Explain the importance of origin of replication' in a replication fork.
✓
Answer
- Replication of DNA occurs in small replication forks, because DNA is such a long molecule that the separation of the two strands along its entirelength requires a very high amount of energy.
- DNA polymerase can catalyse the polymerization of nucleotides only in 5' → 3' direction.
- So on the template strand with 3' → 5' polarity, DNA replication is continuous.
- On the template strand with 5' → 3' polarity, DNA synthesis occurs in short stretches as the opening of replication fork continues; later these short stretches are joined by the action of DNA ligases .
- Replication of DNA does not initiate randomly, and DNA polymerases on their own cannot initiate replication.
- So, there is a specific sequence on DNA, called origin of replication; DNA polymerase bindsto it and continues the process.
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