Write a explanatory note on $DNA$ Fingerprinting
$DNA$ fingerprinting is a very quick way to analyse the differences in the $DNA$ sequences of two individuals.
It involves the identification of differences in repetitive $DNA.$
Repetitive $DNA$ is a specific region in $DNA$ in which a small stretch of $DNA$ is repeated many times.
Through density gradient centrifugation these repetitive $DNA$ are separated from the bulk genomic $DNA.$
Bulk $DNA$ forms a major peak during centrifugation and the other small peaks are known as satellite $DNA.$
These sequences do not code for any proteins normally, but they constitute a large portion of human genome.
The satellite $DNA$ is classified into many categories such as microsatellites, minisatellites etc. on the basis of length of segment, number of repetitive units the base composition ($A$ : $T$ - rich or $\mathrm{G}: \mathrm{C}$ - rich ) etc.
The satellite $DNA$ also show high degree of polymorphism and forms the basis of $DNA$ fingerprinting.
Polymorphism : It is the variation in individuals at genetic level.
Polymorphism arises due to mutations.
It plays an important role in evolution and speciation.
In a population, if an inheritable mutation is observed at high frequency, it is referred to as $DNA$ polymorphism.
There are different types of polymorphism from single nucleotide change to large scale changes.
In an individual, $DNA$ from every tissue (eg., blood, hair follicle, skin, bene, saliva etc.) shows the same degree of polymorphism.
- Thus, they become very essential identification tool in forensic applications.
- As polymorphisms are inherited from parents to children.
So it is useful in paternity testing.
- Technique of $DNA$ Fingerprinting : Alec Jeffreys initially developed $DNA$ fingerprinting also known as $DNA$ typing or $DNA$ profiling to find out markers for the inherited diseases.
He used a satellite $DNA$ as probe that shows very high degree of polymorphism and called it variable number of Tandem Repeats ($VNTRs$).
- The technique involved southern blot hybridisation using radiolabelled $VNTR$ as a probe.
The technique has the following steps :
$(i)$ $DNA$ isolations: $DNA$ is extracted from the cells in a high speed centrifuge.
$(ii)$ Amplification : Amplification many copies of the extracted $DNA$ can be made by the use of polymerase chain reaction.
$(iii)$ Digestion: Digestion of $DNA$ by restriction endonucleases.
$(iv)$ Separation : Separation of $DNA$ fragments by electrophoresis.
$(v)$ Southern Blotting : Transfer of separated $DNA$ fragments to synthetic membranes (like nylon or nitrocellulose).g
Which of the following statement forms the basis of $DNA$ fingerprinting?
In $DNA$ fingerprinting which of the following is true?
Which process is used for amplification or multiplication of $DNA$ for finger printing?
$DNA$ fingerprinting method is very useful for:
One of the most frequently used techniques in $DNA$ fingerprinting is