4. The diagram represents a short section of a DNA molecule undergoing replication.
[VISUALIZATION: Diagram showing a DNA double helix partially unwound by helicase (labelled). One strand shows continuous synthesis by DNA polymerase (labelled) moving towards the replication fork. The other strand shows discontinuous synthesis away from the fork, though Okazaki fragments need not be explicitly shown or labelled for SL. Show nucleotides being added.]
(a) Identify the enzyme labelled that unwinds the DNA double helix. [1]
(b) Explain the role of complementary base pairing in DNA replication. [3]
(c) Distinguish between DNA and RNA in terms of their structure. [2]
Question
Identify the enzyme labelled that unwinds the DNA double helix. [1]
Hint
Hint
Hint
Refer to the diagram description or recall the enzyme responsible for separating DNA strands.
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Question
Explain the role of complementary base pairing in DNA replication. [3]
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Hint
Think about how A pairs with T and G pairs with C, and why this is crucial for making accurate copies.
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Complete Answer
Complementary base pairing (A-T, G-C) ensures each original strand acts as a template for the synthesis of a new strand, leading to the accurate formation of two identical DNA molecules (semi-conservative replication).
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Distinguish between DNA and RNA in terms of their structure. [2]
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Consider the number of strands, the type of sugar, and the nitrogenous bases present in each molecule.
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DNA is double-stranded, contains deoxyribose sugar, and has thymine (T). RNA is single-stranded, contains ribose sugar, and has uracil (U).
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