Polymerase Chain Reaction

Polymerase Chain Reaction (PCR)

A technique used to rapidly amplify a specific region of DNA by making millions of copies.

DNA Primers

Short DNA sequences complementary to the 25-base sequence at the 3’ end of each DNA strand, used to initiate DNA synthesis.

Denaturation

The process in PCR where DNA strands are separated by heating to 95 degrees, breaking the hydrogen bonds between nucleobases.

Annealing

The step in PCR where the temperature is lowered to 55 degrees, allowing primers to bind to the complementary region of DNA.

TAQ Polymerase

An enzyme used in PCR that extends the primers by adding nucleotides at 72 degrees, in both directions.

PCR Machine

Equipment capable of cycling between different temperatures rapidly to facilitate denaturation, annealing, and extension steps in PCR.

Magnesium Chloride (MgCl2)

A co-factor added to PCR tubes to support the activity of DNA polymerase during DNA amplification.

Temperature Effects in PCR:

1st step of PCR

Denaturation of DNA strands.

Temperature is raised to 95-100 degrees

2nd step of PCR

Annealing of primers to DNA.

Temperature is lowered 50 degrees

3rd step of PCR

Extension of primers by TAQ polymerase.

Temperature is raised to 72 degrees