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Question : Describe the steps involved in DNA finger printing.

Answer»

Solution :Steps in DNA Finger printing `:`
(i) Extraction of DNA `:` The process of DNA fingerprinting starts with obtaining a sample of DNA from BLOOD, semen, vaginal fluids, hair roots,teeth, bones, etc.,
(ii) Polymerase chain reaction (PCR) `:` In many situtations, there is only a small amount of DNA available for DNA fingerprinting. If needed many copies of the DNA can be produced by PCR (DNA amplification).
(iii) Fragmenting DNA`:` DNA is treated with restriction enzymes which cut the DNA into smaller fragments at specific sites.
(iv) Separation of DNA by electrophoresis`:` During electrophoresis in an agarose ge, the DNA fragments are separated into bands of different sizes. The bands of separated DNA are sieved out of the GEL using a nylon membrane (treated with chemicals that allow for it to break the hydrogen bonds of DNA so there are single strands).
(v) Denaturing DNA`:` The DNA on gels is denatured y using alkaline chemicals or by heating.
(vi) Blotting`:` The DNA band pattern in the gel is transferred to a thin nylon membrane placed over the .size fractioned DNA strand. by Southern blotting.
(vii) Using probes to identify specific DNA`:` A radioactive probe (DNA labeled with a radioactive substance) is added to the DNA bands. The probe attaches by BASE pairing to those restriction fragments that are complementary to its sequence. The probes can also be prepared by using either .fluorescent substance. or .radioactive isotopes..
(viii) Hybridization with probe `:` After the probe hybridizes and the excess probe washed off, a photographic FILM is placed on the membrane containing .DNA hybrids..
(ix) Exposure on film to make a GENETIC/DNA Fingerprint `:` The radioactive label exposes the film to form an image (image of bands) corresponding to specific DNA bands. The thick and thin dark bands form a pattern of bars which constitutes a genetic fingerprint.


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