1.2 replication of DNA Flashcards
1
Q
Describe the six stages of replication
A
- a DNA strand unwinds
- hydrogen bonds between complementary bases break
- the two strands separate to form two template strands
- free nucleotides attract and line up with their complementary bases
- nucleotides are added by DNA polymerase
- two new identical strands are formed and rewinds
2
Q
What direction does DNA polymerase add nucleotides
A
5’ to 3’
3
Q
Leading strand
A
Synthesised from 5’ to 3’ towards the fork
4
Q
Lagging strand
A
Synthesised in the opposite direction of the fork
Many primers attach along the stand and are extended by DNA polymerase
Smaller fragments of DNA are joined together by DNA ligase
5
Q
What is the function of replication bubbles
A
Speed up the replication process
6
Q
What must be present for DNA replication to take place
A
- ATP
- parental DNA strand and supply of nucleotides
- primers
- enzymes (DNA ligase and DNA polymerase
7
Q
What is PCR
A
Polymerase chain reaction / artificial copy of DNA
8
Q
Is PCR sensitive
A
Is a temperature sensitive reaction
9
Q
Explain the 3 cycles of PCR
A
- denaturing
DNA is heated 92-98 degrees C for a few seconds which separates strands - annealing
DNA is cooled to 50-65 degrees C which allows the short primers to bond to separated DNA strands to a complementary sequence - extending
DNA is heated to 70-80 degrees C for a few minutes which allows heat tolerant DNA polymerase to add bases to the strand by replicating the region of DNA
10
Q
How many times is PCR repeated
A
20-30 cycles
11
Q
What is required for PCR to take place
A
- free nucleotides
- heat tolerant DNA polymerase
- sequence specific primers
