5. The diagram shows the process of DNA replication at a replication fork.
[VISUALIZATION: Diagram of a DNA replication fork. Show the parent DNA double helix unwinding. Label the leading strand being synthesized continuously towards the fork and the lagging strand being synthesized discontinuously away from the fork in Okazaki fragments. Label Helicase, DNA Polymerase III, RNA primer, Okazaki fragment, and indicate the 5′ and 3′ ends of the parent strands and newly synthesized strands to show directionality.]
(a) State the function of helicase in DNA replication. [1]
(b) Distinguish between the synthesis of the leading strand and the lagging strand using **two** features. [2]
(c) Explain the role of complementary base pairing in ensuring the fidelity of DNA replication. [2]
Question
State the function of helicase in DNA replication. [1]
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Think about what needs to happen to the double helix before replication can begin.
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Unwinds/unzips the DNA double helix / breaks hydrogen bonds between bases.
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Question
Distinguish between the synthesis of the leading strand and the lagging strand using **two** features. [2]
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Consider the direction of synthesis relative to the replication fork and whether synthesis is continuous or fragmented.
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Leading strand synthesized continuously towards the replication fork; Lagging strand synthesized discontinuously (in Okazaki fragments) away from the replication fork. Lagging strand requires multiple RNA primers, leading strand only one.
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Explain the role of complementary base pairing in ensuring the fidelity of DNA replication. [2]
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Recall the specific base pairing rules (A with T, C with G) and how this guides the addition of new nucleotides.
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A pairs only with T, and C pairs only with G. Each parent strand serves as a template, ensuring the new strand has a complementary sequence, thus maintaining the genetic information accurately.
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