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"Describe how genetic fingerprinting is carried out? (example of 6-mark question)"

Genetic fingerprinting or DNA fingerprinting is used to detect several different numbers of repeats of minisatellites in a DNA that generate different patterns of DNA bands. Each individual has a unique DNA or genetic fingerprint.

1.     This process is carried out by first isolating the DNA from the blood or hair of a person.

2.     Then, this DNA can be amplified with the help of polymerase chain reaction (PCR).

3.  The DNA is cut with restriction enzymes that result in various DNA strands of different lengths.

4.   The DNA pieces are then separated from each other with the help of gel electrophoresis in which DNA is loaded on a gel. This gel is under an electric field, and the negatively charged DNA migrates towards the positive anode. The larger DNA bands have more molecular weight, thus will travel slower. The smaller bands with lighter weight will travel faster.

5.    Then, these separated DNA strands are transferred to a membrane which is then exposed to complementary radioactive labelled probes. The minisatellites will be attached with these probes and then they can be visualized.

6.    The process of visualization can be done with X-ray radiations by the probes on the X-ray film.

7.   The patterns developed on the film can give us a genetic fingerprint, unique to different individuals. This is because all individuals have different repeats of minisatellites with different sizes. Hence, when cut with restriction enzymes at different restriction sites, DNA bands with varying lengths are produced.

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