I would also like to briefly explain the PCR protocol, in which I read about last week. PCR (Polymerase Chain Reaction) is a common used technique to amplify a specific piece of DNA (to clone a strain of DNA). PCR involves in 3 processes, each requires a specific temperature:
After putting the prepared solution into a Thermal cycler...
1) Denaturing: Under 95℃, the double helix DNA was separated into 2 single strands.
2) Annealing: The temperature quickly cools down to 55-65℃, attaching two primers (forward primer and backward primer) to the end of each strand of DNA. A primers is a strand of nucleic acid that serves as a starting point for DNA synthesis and it is required because the enzymes that catalyze DNA replication, DNA polymerases, can only add new nucleotides to an existing strand of DNA.
3) Elongation: The temperature is then increased to 72℃, catalyzing the polymerase synthesis of DNA.
Each 95℃-60℃-72℃ counts as a cycle, and the amplification usually runs about 30 cycles. By the end of the whole process, an single piece of DNA can be amplified up to a billion strands within just a few hours.
Retrieved from Pray, L. (2008) The biotechnology revolution:
PCR and the use of reverse transcriptase to
clone expressed genes. Nature Education 1(1)
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In the end, we insert the plasmid into the bacteria. In order to keep the foreign DNA inside bacteria, the scientists also include the DNA responsible for antibiotic-resistance in the plasmid and raise the bacteria in antibiotic environment, so the bacteria would need to keep the plamid in order to survive. (I think this was really clever!)
Another excellent post, Peggy! I am quite impressed that you added extra information on an "off week." I am very eager to follow your progress in the future!
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