Unit 1.2: Replication of DNA

Question 1

What does semi-conservative replication mean?

Answer 1

1 strand of the new DNA comes from the original DNA molecule and 1 strand is newly synthesised

Question 2

What are the 5 steps of replication?

Answer 2

1. Helix is unwound by DNA polymerase and hydrogen bonds between bases are broken
2. Primers join to the 3’ end of the leading strand
3. DNA polymerase adds free DNA nucleotides to synthesise a complementary strand continuously
4. On lagging strand primers add one by one and DNA is added in fragments
5. Fragments are joined together by Ligase

Question 3

What are the 5 requirements for DNA replication?

Answer 3

1. DNA template
2. Supply of DNA nucleotides
3. Supply of energy
4. Enzymes
5. Primers

Question 4

Why is a DNA template needed for replication?

Answer 4

It provides the code to copy

Question 5

Why is a supply of DNA nucleotides needed for DNA replication?

Answer 5

To build the new strand of DNA

Question 6

Why is a supply of energy needed for DNA replication?

Answer 6

To provide the enzymes with energy

Question 7

Why are enzymes needed for DNA replication?

Answer 7

DNA polymerase - pair up free DNA nucleotides

Ligase - join up fragments

Question 8

Why are primers needed for DNA replication?

Answer 8

To provide a starting point for the attachment of nucleotides by DNA polymerase

Question 9

What is PCR used for?

Answer 9

Using DNA replication to amplify a specific section of DNA

Question 10

What happens during the 3 stages of PCR?

Answer 10

Stage 1 - 92-98 - hydrogen bond break and strand separate
Stage 2 - 50-65 - primers bind to specific target DNA sequences
Stage 3 - 70-80 - Heat tolerant DNA polymerase activity replicates DNA region to be copied