stages of DNA replication (and PCR)

Question 1

What is PCR?

Answer 1

This is a laboratory technique that is used to amplify specific target sequences of DNA.

Question 2

What is thermal cycling?

Answer 2

This involves cycles of heating and cooling (thermal cycling) to process small quantities of DNA to amplify them.

Question 3

What do we mean by ‘Amplifying?’

Answer 3

The production of multiple copies of DNA sequences.

Question 4

What does PCR involve?

Answer 4

PCR involves separating the DNA strands at a target site and replicating this multiple times.

Question 5

Name 3 applications of PCR?

Answer 5

▪ Forensics
▪ Paternity Tests
▪ Genetic Mutation Screening

Question 6

what’s stage one of PCR

Answer 6

The DNA is taken to between 92- 98oC which separates the strands.
High temperatures - disrupt the hydrogen bonds that bind complimentary base pairs.

Question 7

what’s stage two of PCR

Answer 7

The DNA is then cooled between 50- 65oC allowing complimentary primers to bind to specific target sequences.
Primers bind to the 3’ end on each DNA template at the start of the sequence to be replicated

Question 8

what’s stage three of PCR

Answer 8

Temperature then raised 70-80oC where, heat-tolerant DNA polymerase is used to synthesis new strands from free DNA nucleotides.
This temp is optimum for the polymerase. This is used as it can withstand the higher temp’s during repeated thermal cycles.

Question 9

Why is this process repeated 25-35 times?

Answer 9

To produce many millions of copies.

Question 10

What does gel electrophoresis produce?

Answer 10

A unique DNA profile (or finerprint) of an individual, showing a distinct pattern
(ladder) of all the alleles they possess.