‘There is a paternity dispute for a child'. Which technique can solve the problem. Discuss the principle involved.
$DNA$ finger printing is used to solve the paternity dispute. $DNA$ fingerprinting involves identifying differences in some specific regions in $DNA$ sequence called as repetitive $DNA$, because in these sequences, a small stretch of $DNA$ is repeated many times. These repetitive $DNA$ are separated from bulk genomic $DNA$ as different peaks during density gradient centrifugation.
The bulk $ DNA$ forms a major peak and the other small peaks are referred to as satellite $DNA$. Depending on base composition ($A$ : $T$ rich or $G$: $C$ rich), length of segment, and number of repetitive units, the satellite $DNA$
is classified into many categories, such as micro-satellites, mini-satellites etc. These sequences
normally do not code for any proteins, but they form a large portion of human genome.
These sequence show high degree of polymorphism and form the basis of $DNA$ fingerprinting. Since $DNA$ from every tissue (such as blood, hair- follicle, skin, bone, saliva, sperm etc.), from an individual show the same degree of polymorphism, they become very useful identification tool in forensic applications. Further, as the polymorphisms are inheritable from parents to children, $DNA$ fingerprinting is the basis of paternity testing, in case of disputes.
The technique of $DNA$ fingerprinting was initially developed by Alec Jeffreys. Lalji Singh is called father of Indian $DNA$ fingerprinting or $DNA$ profiling or $DNA$ typing. He used a satellite $DNA$ as probe that shows very high degree of polymorphism. It was called as Variable Number of Tandem Repeats ($VNTR$).
The technique, as used earlier, involved Southern blot hybridisation using radiolabelled $VNTR$ as a probe. It included
$(i)$ 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, such as nitrocellulose or nylon,
$(v)$ Hybridisation using labelled $VNTR$ probe, and $(vi)$ Detectionof hybridised $DNA$ fragments by autoradiography.
In Southern blotting......... is separated by gel electrophoresis:
The commonly used $DNA$ fingerprinting technique in forensic studies is simply a method involving
$DNA$ finger printing technique was first developed by
A technology, which has found immense use in solving cases of disputed parentage, is
List the various markers that are used in $DNA$ finger printing.