Question

Name and describe the technique that will help in solving a case of paternity dispute over the custody of a child by two different families.

Two blood samples, A and B, picked up from the crime scene were handed over to the forensic department for genetic fingerprinting. Describe how the technique of genetic fingerprinting is carried out. How will it be confirmed whether the samples belonged to the same individual or to two different individuals?

A burglar in a huff forgot to wipe off his blood stains from the place of crime where he was involved in a theft and a fight. Name the technique which can help in identifying the burglar from the blood stains. Describe the technique.

Answer 1

The technique used in all three cases is DNA Fingerprinting (or Genetic Fingerprinting), which identifies individuals based on unique sequences called VNTRs. The process begins with DNA extraction from samples like blood or tissue, followed by PCR amplification to increase the DNA quantity if the sample is small. The DNA is then digested into fragments using restriction enzymes and separated by size through gel electrophoresis. These fragments are transferred to a nylon membrane (Southern Blotting) and treated with radioactive DNA probes that bind to specific VNTR sequences (Hybridisation). Finally, autoradiography produces an X-ray film showing a unique pattern of dark bands, known as a DNA fingerprint.

In a paternity dispute, this helps because a child’s banding pattern is a 50-50 combination of their biological parents’ patterns; by matching the child’s bands to the families, the true parents are identified. For crime scene samples or identifying a burglar, forensic experts compare the banding patterns of the samples found at the scene with those of the suspects. If the position, size, and number of bands are identical, the samples belong to the same individual, whereas any difference in the pattern proves they belong to different people.