“DNA replication is continuous and discontinuous on the two strands within the replication fork.” Explain with the help of a schematic representation.
Ans.
In DNA replication, the synthesis of new DNA strands occurs in both continuous and discontinuous manner on the two strands within the replication fork. This process is known as semi-discontinuous replication. Here’s an explanation with the help of a schematic representation:
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Leading Strand:
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The leading strand is synthesized continuously in the 5′ to 3′ direction toward the replication fork.
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DNA polymerase synthesizes the new strand by continuously adding nucleotides complementary to the template strand.
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As the replication fork opens up, the leading strand template is continuously exposed, allowing continuous DNA synthesis (see figure).
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Lagging Strand:
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The lagging strand is synthesized discontinuously in the 5′ to 3′ direction away from the replication fork.
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DNA polymerase synthesizes short fragments of DNA, known as Okazaki fragments, in the direction away from the fork.
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These fragments are synthesized in the direction opposite to the movement of the replication fork, resulting in discontinuous synthesis.
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The Okazaki fragments are later joined together by DNA ligase to form a continuous strand (see figure).
