What is DNA profiling?(b) Arrange the following steps of DNA profiling in correct sequence:(i) Selection of DNA probe; (ii) Isolation of DNA(iii) Gel electrophoresis; (iv) Hybridization(v) Southern blotting; (vi) Restriction digestion

Answer:

(a) DNA profiling (DNA fingerprinting): it is a technique of identifying individuals by comparing the pattern of their repetitive DNA sequences. About 99.9% of human DNA is identical, but short repetitive sequences such as VNTRs (variable number of tandem repeats, minisatellites) vary in number from person to person. When these are cut, separated and probed, every person (except identical twins) gives a unique band pattern. It was developed by Alec Jeffreys and is used in forensic science, paternity / maternity disputes, identification of bodies and in studying evolution and population genetics.

(b) Correct sequence:

1. (ii) Isolation of DNA
2. (vi) Restriction digestion
3. (iii) Gel electrophoresis
4. (v) Southern blotting
5. (i) Selection of DNA probe
6. (iv) Hybridization

i.e. (ii) → (vi) → (iii) → (v) → (i) → (iv). After hybridization, the bands are detected by autoradiography and compared.