DNA REPLICATION Flashcards
1
Q
when does rep occur
A
during S phase of mitosis
2
Q
what type of replication occurs
A
semiconservative
3
Q
4 main steps of Rep
A
- initiation
- primer binding
- elongation
- termination
4
Q
explain initiation
A
- DNA helicase bind to origin of replication and unwinds double helix (break H bonds)
- replication fork
- both strands used as template strands
5
Q
explain primer binding
A
- short RNA primer binds to single strands
- nucleotides only added to 3’ end of exisitng nucleotide chain
6
Q
explain elongation
A
- 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
7
Q
what is the lagging strand
A
- 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)
8
Q
explain termination
A
- polymerase I removes RNA primer with DNA
- DNA ligase binds fragments to form one continuous strand
9
Q
what happens if there is an error in base pairing during DNA rep?
A
DNA pol III proofreads and will correct errors
10
Q
what is PCR
A
polymerase chain reaction
- used to amplify a small amount of DNA
