DNA replication

Question 1

What are the two processes of cell division?

Answer 1

Nuclear division ( nucleus) 
Cytokinesis ( cytoplasm)

Question 2

What is semi conservative replication?

Answer 2

How strands of DNA replicate

Question 3

What is the process of semi-conservative replication?

Answer 3

• DNA helicase breaks h bonds in DNA
• Double helix separates and unwinds
• exposed nucleotides become templates to which free complimentary nucleotides join by specific base pairing
• joined in a condensation reaction catalysed by DNA polymerase

Question 4

Why does DNA polymerase work in opposite directions?

Answer 4

• DNA strands are antiparallel to each other
• So the nucleotides are aligned differently
• Enzyme DNA [polymerase has active site of a specific shape
• only phosphate end can bind with DNA polymerase

Question 5

Which two theories explain how DNA replication works?

Answer 5

• Conservative model. Original model of DNA stays in tact separate daughter DNA made of different molecules
• Semi-conservative model where DNA molecule splits in two and is replicated in its mirror image

Question 6

How were the models of DNA replication tested?

Answer 6

• All bases have nitrogen
• nitrogen how two forms, light N14 and heavy N15
• Bacteria incorporate their growing medium into their new DNA they make
• original bacteria contained only N15
• it was added to medium of N14 and allowed to replicate once
• then passed through centrifuge to extract each strand of DNA and see where it collected in the tube
• this was repeated once more
• after two generations no bacteria had N15 DNA only