What is an example of polymerase chain reaction?

Answer 1

Polymerase chain reaction (PCR) is used to amplify nucleic acids. It was invented in its current form by Kary Mullins in 1983/1986.

The template (DNA or RNA) is duplicated by a thermostable DNA polymerase - originally from Thermus aquaticus - using sequence specific primers (short single-strand oligonucleotides) that are designed to sit on either side of the piece of template that is to be amplified.

Changes in temperature are used to move through the different stages required to duplicate the DNA.

• 95°C denatures DNA to two single strands.
• The temperature is decreased to ~50-60°C to allow the primers to anneal (bind) to the 5' end of the DNA templates - the exact temperature is 5°C lower than the primer's sequence-determined melting point (Tm). At the melting point half of the dissolved primers in solution would be annealed to the template DNA.
• The temperature then climbs to 72°C where the polymerase adds dNTPs to the 3' end of the primer - most commercial DNA polymerases can elongate 1000 bases per minute. Some have "proof-reading" activity, where it can correct a wrong base it may have inserted. If the template is RNA then a reverse transcriptase is used - it reads the RNA, but makes DNA.
• The reaction is heated again to 95°C to restart the cycle. After the last cycle the reaction is held at 72°C for a few minutes to ensure that all the strands are fully elongated.

Each cycle duplicates the template, meaning an exponential increase in the amount of the target sequence. Usually, 30 cycles produce sufficient DNA for downstream applications. More cycles may produce more, but at some point the enzyme becomes less efficient or the dNTPs run out.

Answer 2

if some one does a regular chain reaction