Which among the following is the basis of paternity testing, in case of disputes ?

DNA fingerprinting .

The basis of paternity testing, particularly in cases of disputes, primarily relies on a technique known as "DNA fingerprinting."

DNA fingerprinting, also called DNA profiling or DNA typing, is a forensic technique used to identify individuals based on their unique DNA characteristics.

The technique of DNA Fingerprinting was initially developed by Alec Jeffreys. 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.