Question

Raghu is married to Radha, who was previously married to Varun, now deceased. Varun and Radha conceived one child together and adopted one child. Raghu and Radha have also conceived one child. All members of Radha's current family have had DNA fingerprinting done. Unfortunately the sheet that identified each child has been misplaced. Identify which fingerprint in each lane corresponds to each child.

Answer 1

Hint:DNA fingerprinting is a technique used to identify sequences in certain parts of the DNA. Most of the DNA material is common for all human beings but certain regions are unique for every individual. This region has 2 alleles which are inherited. Children acquire 50 % of this region from mother and other 50% from father. Hence, a child’s DNA pattern is a combination of his parent’s DNA.

Complete answer:
In DNA fingerprint testing the DNA samples from parents and children are extracted and sent to the laboratory. The samples are processed. Profiling os samples is done by PCR or RFLP techniques. Using Restriction fragment length polymorphism the DNA samples are cut on certain sites by restriction endonucleases. DNA probes are used to identify these separated fragments at a specific gene locus. This takes place on a Nylon membrane which is then placed on film. After development, visible band patterns are observed which matches half with the mother and half with the father.

Two allele bands are seen in case of child 2 matching Radha and Raghu. This means child 2 belongs to Raghu and Radha.
Child 3 has alleles matching Varun and Radha which means they are child 3’s parents.
Child 1’s allele matches neither with Varun nor with Radha. Hence, child 1 is adopted one.
Additional Information:
-DNA profiling is used in forensic sciences to solve crimes like murder and rapes.
-DNA fingerprinting is used in paternity and maternity tests where the biological parenthood of a child is disputed.
-RFLP is used as it is more accurate than PCR.

Note:Short tandem repeats or STRS are markers used by scientists nowadays to identify individuals using DNA fingerprinting. They are unique and occur repetitively in different patterns in different individuals.