Which of the following is the basis of paternity testing, in case of…

The correct answer is Option (3) → DNA fingerprinting.

A paternity test must compare the DNA of different people. Some short DNA sequences are repeated many times in our genome, and the number of repeats differs from person to person. This variation is called polymorphism, and a child inherits it from both parents.

Option (1) Expressed Sequence Tags. — Incorrect. Expressed Sequence Tags (ESTs) are one approach of the Human Genome Project: identifying all the genes that are expressed as RNA. They find genes; they do not compare two people.

Option (2) Sequence Annotation. — Incorrect. Sequence annotation is the other approach of the Human Genome Project: sequencing the whole genome and later assigning functions to its regions. It does not test who is related to whom.

Option (3) DNA fingerprinting. — Correct. DNA fingerprinting compares the repetitive DNA of individuals. As these polymorphisms are inherited from parents to children, the child’s pattern matches partly the mother’s and partly the true father’s.

NCERT Extract:
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.”
Human Genome Project – “… Methodologies : The methods involved two major approaches. One approach focused on identifying all the genes that are expressed as RNA (referred to as Expressed Sequence Tags (ESTs). The other took the blind approach of simply sequencing the whole set of genome that contained all the coding and non-coding sequence, and later assigning different regions in the sequence with functions (a term referred to as Sequence Annotation).”