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NSWBiologyQuick questions
Module 5: Heredity
Quick questions on DNA replication explained: HSC Biology Module 5
8short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is 1. Unwinding?Show answer
The enzyme helicase breaks the hydrogen bonds between base pairs, separating the double helix into two single strands at the replication fork.
What is 2. Priming?Show answer
Primase synthesises a short RNA primer on each single strand, giving DNA polymerase a free 3'-OH group to extend from.
What is 3. Elongation?Show answer
DNA polymerase reads each template strand in the 3' to 5' direction and adds complementary free nucleotides to the growing daughter strand in the 5' to 3' direction.
What is 4. Ligation?Show answer
DNA ligase joins the Okazaki fragments into one continuous strand.
What are wrong base pairs?Show answer
A pairs with T (DNA) or U (RNA). G pairs with C. Get this wrong and you lose 1-2 marks immediately.
What is q1?Show answer
A short DNA template reads 3'-TACGGCATTAGC-5'. Write the sequence of the newly synthesised daughter strand, indicating the 5' and 3' ends. [2 marks]
What is q2?Show answer
Predict the result of the Meselson-Stahl experiment after two rounds of replication in normal medium, given the parental DNA was fully labelled with . [3 marks]
What is q3?Show answer
A drug candidate inhibits DNA ligase activity in dividing cells. (a) Describe how this drug would affect DNA replication at the molecular level. (b) Explain why this drug would have a greater effect on rapidly dividing cells such as bone marrow than on neurons.