PCR- The Polymerase Chain Reaction

Question 1

What is PCR?

Answer 1

Using DNA replication to amplify (make many copies) a specific section of DNA, using a series of temperature changes called thermal cycling

Question 2

What happens during the 1st stage of PCR?

Answer 2

DNA strands are separated, as hydrogen bonds between bases are broken

Question 3

What happens during the 2nd stage of PCR?

Answer 3

Primers bind to specific target DNA sequences

Question 4

What happens during the 3rd stage of PCR?

Answer 4

TAQ (heat tolerant) DNA polymerase activity replicates DNA region to be copied

Question 5

In stage 1, why do the strands separate instead of just disintegrating?

Answer 5

Only the weak hydrogen bonds between base pairs are broken as the sugar phosphate bonds are much stronger

Question 6

In stage 2, what is the function of the primers?

Answer 6

• To bind the target DNA sequence being copied

- To allow TAQ polymerase to replicate DNA sequence

Question 7

In stage 3, why is heat tolerant polymerase used?

Answer 7

Normal human polymerase would be denatured by the high temperatures in the first stage. The TAQ polymerase extracted from thermophylic bacterium, which lives in hot volcanic springs, will not be denatured by the high temperature

Question 8

What temperature does stage 1 of PCR take place in?

Answer 8

92°C

Question 9

What temperature does stage 2 of PCR take place in?

Answer 9

55°C

Question 10

What temperature does stage 3 of PCR take place in?

Answer 10

72°C