Describe the first steps that occur when DNA replication begins.

The double helix unwinds and hydrogen bonds between complementary base pairs break, separating the two strands.

What role does each original DNA strand play during replication?

Each original strand acts as a template for the synthesis of a new complementary strand.

How do free DNA nucleotides position themselves during replication?

They align opposite their complementary bases on the template strand following base-pairing rules: adenine pairs with thymine (A-T) and cytosine pairs with guanine (C-G).

In which direction does DNA polymerase add nucleotides to a growing strand?

DNA polymerase adds nucleotides in the 5' to 3' direction only.

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Genes and Health

Semi-conservative replication and Meselson-Stahl

3 things to know
Papers 1, 2 and 3

Overview

Recall questions on the role of DNA polymerase, and on how Meselson and Stahl showed replication to be semi-conservative.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Explain how Meselson and Stahl's results refuted both conservative and dispersive models of replication.

Key term

What is the function of DNA polymerase in DNA replication?

Key term

What does it mean to say that DNA replication is semi-conservative?

Questions from this subtopic

Each one with the model answer underneath.

1
What does it mean to say that DNA replication is semi-conservative?
Model answer
Each new DNA molecule contains one original (parental) strand and one newly synthesised strand.
2
Describe the first steps that occur when DNA replication begins.
Model answer
The double helix unwinds and hydrogen bonds between complementary base pairs break, separating the two strands.
3
What role does each original DNA strand play during replication?
Model answer
Each original strand acts as a template for the synthesis of a new complementary strand.
4
How do free DNA nucleotides position themselves during replication?
Model answer
They align opposite their complementary bases on the template strand following base-pairing rules: adenine pairs with thymine (A-T) and cytosine pairs with guanine (C-G).
5
What is the function of DNA polymerase in DNA replication?
Model answer
DNA polymerase catalyses the formation of phosphodiester bonds between adjacent nucleotides, joining them to form the new strand.
6
In which direction does DNA polymerase add nucleotides to a growing strand?
Model answer
DNA polymerase adds nucleotides in the 5' to 3' direction only.

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