Experiment4-PCR

Experiment4-PCR - Experiment 4 (Lab Period 4) Amplification...

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Experiment 4 (Lab Period 4) Amplification of a specific DNA fragment by the Polymerase Chain Reaction (PCR) Once DNA is extracted from an organism, many different types of analyses can be performed. Biologists are often interested in studying a specific gene or a specific chromosome region to determine how that gene functions at the molecular level. To do this that region containing the gene of interest must be isolated away from the rest of the DNA. Typically, a gene you want to study is composed of 1000 nucleotides of DNA (or less) while most organisms have on the order of 10 7 to 10 9 nucleotides of DNA in each cell. Therefore, unless you are interested in studying the entire DNA complement of an organism, it becomes necessary to go through several steps following DNA extraction to isolate that small fragment of DNA that you actually want to study. The isolation of a specific DNA fragment is frequently achieved by cloning. This is a complex and time-consuming process. To clone a fragment of DNA a biologist has to essentially cut the DNA into many small pieces and sort through all of the pieces to find the one containing the gene in which he or she is interested. In recent years the need to clone a fragment of DNA in every situation has been eliminated by the development of the Polymerase Chain Reaction (PCR) by Kerry Mullis. The advantage of PCR over cloning is that, as we will see below, you can specifically target the gene you want and make many copies of it in a test tube. This means that you do not have to sort through all of the pieces of DNA, you simply target the one you want. Of course you need to know something about the gene from previous work in order to be able to target it specifically, but with recent advances in genome sequencing this information is becoming readily available for most genes. PCR has become widespread since it is much quicker than cloning, and much cheaper. The idea behind PCR is that you exploit the natural system of DNA replication. Every cell
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This note was uploaded on 01/30/2012 for the course BIO 2004 taught by Professor Morton during the Spring '11 term at Columbia.

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Experiment4-PCR - Experiment 4 (Lab Period 4) Amplification...

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