Polymerase chain reaction

[suskieanna]

hello I was a bit confused.. does the PCR involve ligation? If it does, if the exam asks to write down steps for PCR, do I also need to add ligation step? thanks!

[Sine]

hello I was a bit confused.. does the PCR involve ligation? If it does, if the exam asks to write down steps for PCR, do I also need to add ligation step? thanks!

Ligation is the joining of two nucleotide (in this case DNA) strands so I think this is inherent in your answer. You should have a quite robust 4 mark answer for PCR.

•   Heat DNA to about 90C to separate strands
•   Cool to about 50C to anneal/attach primers
•   Heat to about 72C for taq polymerase to copy strands
•   Repeat cycle

This is taken from heidi's VCAA approved biology definitions

[Erutepa]

hello I was a bit confused.. does the PCR involve ligation? If it does, if the exam asks to write down steps for PCR, do I also need to add ligation step? thanks!

PCR does not involve ligation (not interms of the action of DNA ligase atleast).
The steps relevant are:
1. Denaturation to separate DNA into single strands (92 degrees)
2. Annealing of the primers (50-60 degrees) (just pick one temp)
3. Extension from the primers by Taq polymerase (72 degrees (optimum temperature of Taq polymerase)
This cycle doubles the amount of DNA.
The process is continued until the desirable amount of DNA is achieved.