Question

1. What is RFLP (restriction fragment length polymorphisms)? Explain how RFLPs are used as one of the tools for “Fingerprinting” of an individual’s DNA.

Answer 1

• Restriction fragment length polymorphism (RFLP) is a method which would exploit the polymorphisms (a variation in homologous DNA sequences) in order to distinguish individuals or to point out the location of genes within a sequence.
• In RFLP analysis, a DNA sample is digested into fragments using restriction enzymes and the resulting restriction fragments are separated using gel electrophoresis according to their size.

RFLPs are used as one of the tools for Fingerprinting of an individual’s DNA.

• The principle of RFLP in DNA fingerprinting is that any genomic DNA can be differentiated according to the presence or absence of restriction enzyme sites.DNA is unique to an individual so we can use DNA fingerprinting to match genetic information.The restriction fragment length polymorphism method cut out genes which are likely to be differentiating factors using restriction enzymes.

PROCEDURE OF DNA FINGERPRINTING BY RFLP METHOD:-

1. Obtain a sample of cell (skin, hair, blood cells which contain DNA). The DNA is extracted from the cells and purified.
2. The DNA is then cut at specific points restriction enzymes.The enzymes produced fragments of varying lengths that were sorted by placing them on a gel and then subjecting the gel electrophoresis.
3. The sorted double stranded DNA fragments are then subjected to a blotting technique.Here they were split into single strands and transferred to a nylon sheet.
4. The fragments undergoes autoradiography by which they were exposed to DNA probes.A piece of X-ray film was then exposed to the fragments and a dark mark was produced at any point where a radioactive probe had become attached.The resultant pattern of marks could be analyzed.