QUESTION 3 (4 marks)
Explain the role of the enzymes helicase and DNA polymerase in the process of DNA replication.
QCAA guide · typeset solution
QCAA sample response and mark allocation
3 | Helicase unzips the DNA molecule by breaking the weak hydrogen bonds between the two complementary strands. This creates a replication fork region so that bases are exposed. DNA polymerase uses each original strand as a template to produce a copy of the DNA molecule, and adds complementary nucleotides to the exposed bases. DNA polymerase also proofreads the newly synthesised strand. | • states helicase’s role in unzipping DNA [1 mark] exposing bases [1 mark] • states DNA polymerase’s role in adding complementary nucleotides to the exposed bases [1 mark] • states another role of helicase, polymerase, or suitable feature of the process [1 mark] | Other suitable roles or features include: DNA polymerase proofreading the new strand or other suitable response consistent with a reasonable understanding. | ||
QCAA sample response and marking criteria reproduced from the official guide.
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