DNA REPLICATION

Question 1

when does rep occur

Answer 1

during S phase of mitosis

Question 2

what type of replication occurs

Answer 2

semiconservative

Question 3

4 main steps of Rep

Answer 3

1. initiation
2. primer binding
3. elongation
4. termination

Question 4

explain initiation

Answer 4

• DNA helicase bind to origin of replication and unwinds double helix (break H bonds)
• replication fork
• both strands used as template strands

Question 5

explain primer binding

Answer 5

• short RNA primer binds to single strands
• nucleotides only added to 3’ end of exisitng nucleotide chain

Question 6

explain elongation

Answer 6

• DNA nucleotides added to primer by DNA polymerase III
• pol reads in 3’ to 5’ but synthesises in 5’ to 3’ direction
• adding NTPs: dATP, dGTP etc

Question 7

what is the lagging strand

Answer 7

• DNA iis read in 3’ to 5’ directon, so pol would keep meeting end of strand for one side
• okazaki fragments are added on (discontinuous DNA rep)

Question 8

explain termination

Answer 8

• polymerase I removes RNA primer with DNA
• DNA ligase binds fragments to form one continuous strand

Question 9

what happens if there is an error in base pairing during DNA rep?

Answer 9

DNA pol III proofreads and will correct errors

Question 10

what is PCR

Answer 10

polymerase chain reaction
- used to amplify a small amount of DNA