Write an explanatory note on $DNA$ Fingerprinting.

(N/A) $DNA$ fingerprinting is a rapid method for comparing the $DNA$ sequences of any two individuals.
It involves identifying differences in specific regions of the $DNA$ sequence known as repetitive $DNA$,where a small stretch of $DNA$ is repeated many times.
These repetitive sequences are separated from bulk genomic $DNA$ as distinct peaks during density gradient centrifugation. The bulk $DNA$ forms a major peak,while the smaller peaks are referred to as satellite $DNA$.
These sequences typically do not code for proteins but constitute a large portion of the human genome. They exhibit a high degree of polymorphism,which forms the basis of $DNA$ fingerprinting.
Polymorphism (genetic variation) arises due to mutations. If a germ cell mutation is inheritable and does not impair reproductive ability,it can spread through a population.
$DNA$ polymorphism is defined as the occurrence of more than one variant (allele) at a locus in a human population with a frequency greater than $0.01$.
Technique: Developed by Alec Jeffreys,it uses satellite $DNA$ as a probe,specifically Variable Number of Tandem Repeats $(VNTR)$.
The process involves:
$(i)$ Isolation of $DNA$.
$(ii)$ Digestion of $DNA$ by restriction endonucleases.
$(iii)$ Separation of $DNA$ fragments by electrophoresis.
$(iv)$ Transferring (blotting) of separated $DNA$ fragments to synthetic membranes (nitrocellulose or nylon).
$(v)$ Hybridisation using a labelled $VNTR$ probe.
$(vi)$ Detection of hybridised $DNA$ fragments by autoradiography.