Question

Write a short note on DNA fingerprinting.

Answer 1

Hint: It is a technique used to identify the parent and child relationship during a dispute. Also, it is a technique used to analyze the DNA for forensic tests and it can further be used to analyze the genetic drift in a population.

Complete step by step answer:
DNA fingerprinting is a technique to determine the link between a biological sample and a suspicious individual. The test DNA sample obtained from a crime area will be compared with the DNA sample of a suspicious individual. If the DNA pattern (number of variable repeats of the satellite DNA) observed between the suspect and the DNA sample obtained from the crime area matches, then the suspicious individual is involved in the criminal activity and vice versa.
 Mini- satellite and microsatellite are repeating DNA sequences, which exhibit high polymorphism.
Minisatellites/Variable number of tandem repeats (VNTR): These are short (10- 60bp) DNA sequences. The repeat length of these variants ranges from 10bp to 100bp. Minisatellites are also known as Variable Number of Tandem repeats because the total number of repeats will highly differ between various persons.  Since microsatellites exhibit high polymorphism, they are used in DNA fingerprinting analysis.
Microsatellites: Microsatellites are short (1- 6 bp) DNA sequences. Microsatellites exhibit high polymorphism and they are used to determine paternity, recombination mapping.

The figure represents the DNA fingerprints of a DNA sample obtained from the crime area and the suspects. In this scenario, the DNA fingerprints obtained from the crime scene and suspect 2 matches, and hence suspect 2 is involved in the crime.
Steps involved in DNA fingerprinting are:
- Isolation of the sample DNA.
- The isolated DNA will be fragmented using restriction enzymes.
- Gel electrophoresis will be performed for the fragmented DNA to separate the DNA fragments.
- The DNA will be blotted in a nylon membrane.
- The DNA fragments that are blotted in a nylon membrane will be hybridized by radioactive VNTR probes.
- The DNA fragments will be analyzed by autoradiography.

Note: The role of microsatellite and minisatellite is not elucidated completely. Till now, it is identified to facilitate the genetic map construction, DNA fingerprinting, and isolation of the genes causing human diseases. Since the length of both micro and minisatellites varies from person to person it is highly efficient to perform DNA fingerprinting.