Today's lesson focuses on the process of gel electrophoresis, which is a process typically used to compare different DNA samples to each other. The basic idea is as follows:
1. A sample of DNA (from a postage stamp, blood sample, skin cell, etc) is combined with restriction enzymes, which cut the full DNA sample into pieces at specific base pair sequences.
2. The sample of pieces is used in a polymerase chain reaction, or PCR. This takes the small pieces of DNA in the sample and creates MANY copies of each piece so that there is enough DNA that the sample can be analyzed.
3. This larger sample of cut DNA pieces is combined with a dye and placed in a gel electrophoresis set-up. By applying a voltage across the gel, the differently sized pieces of DNA are pulled towards the positive side. The smaller pieces move more quickly than the larger pieces. As a result, the different sizes of pieces spread out like runners in a race.
4. The pattern of colored bands is unique and is related to the number of pieces of each size in the original sample of DNA. The number of pieces of each size (and therefore a particular gel pattern) is unique to an individual. By comparing a gel made of an unknown person to gel patterns made of known identities, it is possible to determine the unknown identity.
Here are some videos to help you get it:
The Power of DNA:
Applications of DNA Fingerprinting:
PCR reaction:
DNA fingerprinting again:
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