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Extension Time In Pcr In Collin
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Multi-State
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Collin
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US-0018LTR
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FAQ
If the extension time is too long, secondary products can be formed, which can contribute to smearing. The quality of the template DNA can also affect the appearance of the PCR product on the gel. Degraded DNA can lead to the formation of shorter and larger fragments, which can contribute to smearing.
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.
The final stage is the extension step (20 sec to 1 min at 72 °C), which is performed so that the DNA polymerase extends the primer sequences from the 3' of each primer to the end of the amplicon. A 1 min extension is typically sufficient to synthesize PCR fragments up to 2 kilobases (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 is achieved by using the loosened nucleotides of each base to grow the complementary DNA strand. The end result is two double-stranded products of DNA. The temperature that is used during the extension phase is dependent on the DNA polymerase that is used.
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.
Initial Denaturation for 2 minutes at 94°C. Denature for 30 seconds at 94°C. Anneal primers for 30 seconds at 55°C (or 5°C below Tm). Extend DNA for 2 minutes at 72°C.
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.
