1)why does DNA replication occur in small replication forks not in its entire length? 2)why is DNA replication continuous and discontinuous in a replication fork? 3)explain the importance of "origin of replication" in a replication fork.
1) DNA replication occurs in small replication forks not in its entire length in one time as DNA is a very large molecule and only that part of DNA opens up which is being replicated. Opening of whole DNA molecule would be energetically more expensive process.
2) The main enzyme involved in DNA replication is the DNA-dependent DNA polymerase. This enzyme catalyses the polymerisation of deoxynucleotides along the 5′ → 3′ direction, and hence, replication is continuous along the 3′ → 5′ strand (leading strand) and discontinuous along the template, i.e., the 5′ → 3′ direction (lagging strand).
Okazaki fragments are short DNA segments on the lagging strand, formed in the 5’ – 3’ direction, starting from RNA primers. A separate RNA primer is needed for the synthesis of each Okazaki fragment. These discontinuously synthesized fragments are later joined by the enzyme DNA ligase.
3) Ori stands for Origin of replication. This site has the highly conserved sequence of DNA among various species. The replication of DNA starts here because this site attracts some proteins which help in the opening and unwinding of DNA and this leads to the initiation of replication.
@Monisha, good job!!!