Extension Time In Pcr In Cook
Description
Form popularity
FAQ
A typical PCR cycle includes an extension step at 72°C after denaturation of double-stranded DNA and annealing of oligonucleotide primers. At this temperature the thermostable poly-merase replicates the DNA at an optimal rate that depends on the buffer and nature of the DNA template ( 1 ).
Step : 3 Extension Generally, the reaction mixture is heated to a temperature intermediate between denaturation and annealing at this stage. 72°C is the ideal temperature for Taq polymerase. The polymerase extends the primers from 5' to 3'.
Extension Time Extensions are normally performed at 68°C. As a general rule, use extension times of one minute per 1000 base pairs (e.g. 3 minutes for a 3 kb product) For products less than 1 kb, use 45-60 seconds. Products greater than 3 kb, or reactions using more than 30 cycles, may require longer extensions.
The extension time of PCR depends upon the synthesis rate of DNA polymerase and the length of target DNA. The typical extension time for Taq DNA Polymerase is 1 min/kb, whereas that of Pfu DNA polymerase is 2 min/kb.
The extension rate of Pfu DNA Polymerase is lower than that of Taq DNA Polymerase. Therefore, during the extension step, allow approximately 2 minutes for every 1kb to be amplified (minimum extension time of 1 minute).
Extension/Elongation Step The primers represent the starting point for the next step, called the extension step. During the extension, or elongation, step, Taq polymerase binds to each PCR primer and begins adding nucleotides. Note that Taq, like human DNA polymerase, can only add DNA nucleotides in one direction.
Extension Time Extensions are normally performed at 68°C. As a general rule, use extension times of one minute per 1000 base pairs (e.g. 3 minutes for a 3 kb product) For products less than 1 kb, use 45-60 seconds. Products greater than 3 kb, or reactions using more than 30 cycles, may require longer extensions.
Duration of extension will be dependent upon amplicon size (30 sec per 1 kb). The period of elongation depends upon the desired length of the amplicon and the enzyme used. Since qPCR amplicons are short, this is typically 5–30 sec.
