2.2 DNA replication

Question 1

When does dna replication occur

Answer 1

Before mitosis –> “s” synthesise phase of cell cycle
Before meiosis

Question 2

Where does DNA replication occur

Answer 2

In the nucleus

Question 3

What is required for DNA replication

Answer 3

Double stranded DNA template
Free DNA nucleotides with bases : Adenine, thymine, cytosine, guanine
Enzymes: DNA helicase- breaks the hydrogen bonds
- DNA polymerase - forms phosphodiester bonds
ATP: source of energy

Question 4

How many hydrogen bonds are there between adenine and thymine

Answer 4

2 hydrogen bonds

Question 5

How many hydrogen bonds are there between cytosine and guanine

Answer 5

3 hydrogen bonds

Question 6

What is the first step for DNA replication

Answer 6

DNA helicase breaks hydrogen bonds to separate the strands

Question 7

What is the second step of DNA replication

Answer 7

Free DNA nucleotides bind to exposed bases by complimentary base pairing

Question 8

What is the third step of DNA replication

Answer 8

DNA polymerase catalyses formation of phosphodiester bonds between phosphate and sugar (using ATP) - condensation reaction

Question 9

What is the follow up to the third step of DNA replication

Answer 9

The active site of DNA polymerase is only complimentary to the 3^1 end of the strand, so it can only add nucleotides here and builds the new strand in the 5^1 to 3 direction

Question 10

What is semi-conservative replication?

Answer 10

The original DNA molecule split into two separate strand, each of which then replicated its mirror image. Each of the two new molecules would therefore have one strand of new material and one strand of the original.

Question 11

Semi conservative (shorter definition)

Answer 11

One half of the newly replicated DNA (new) and the other half is from the original strand of DNA