U3A1: 4C polymerase chain reaction (PCR)

Question 1

how does PCR begin

Answer 1

a mixture of a DNA sample, taq polymerase, nucleotide bases and DNA primers are placed into a thermal cycler.

Question 2

purpose of PCR

Answer 2

to amplify a sample of DNA by creating additional copies via thermal cycling.

Question 3

explain first stage of PCR

Answer 3

1. denarutation:
   DNA is heated to 90-95 degrees to break the hydrogen bonds, making single-strand DNA.

Question 4

explain second stage of PCR

Answer 4

2. annealing:
   single-stranded DNA is cooled to 50-55 degrees to allow primers to bind to complementary sequences.

Question 5

explain third stage of PCR

Answer 5

3. elongation:
   DNA is heated to 72 degrees so taq polymerase can work optimally, binding to the primer, acting as a starting point for the synthesis of the new complementary strand of DNA.

Question 6

forward primers

Answer 6

binds to the start codon at the 3’ end of the template strand.
causes taq polymerase to synthesise a new strand of DNA in the same direction RNA polymerase would function.

Question 7

reverse primers

Answer 7

binds to the stop codon at the 3’ end of the coding strand.
causes taq polymerase to synthesise a new strand in the reverse direction that RNA would function.