What is DNA fingerprinting ? Describe various steps involved in DNA Fingerprinting ?

What is DNA fingerprinting ? Describe
various steps involved in the same.
Answer : The technique developed to identif a person with the help of DNA restriction analysis is known as
DNA profiling or DNA fingerprinting

OR

The technology that facilates the identification of individual at genetic level is known as DNA
fingerprint.
  1. It is also known as DNA profiling/ DNA printing / DNA typing
  2. DNA fingerprinting was developed by Alec Jeffreys - british genetists in 1984.
  3. According to this technique, nucleotide Sequence present on DNA is identified. But about 99.9% of nucleotide sequence in all individuals is same. Only some short pieces of nucleotides differ from one person to another person.
  4. These specific sequence of nucleotides 20-100 base pairs are repeated several times on length of DNA. The repetation of these base number are unique in organism.
  5. These sequence of base are called as minisatellite or VNTRs (variable number of tandem repeats).
  6. Each organism transmit such repeats to next generation which are used as genetic marker in personal identifing test.

Steps involve in making DNA fingerprinting:

A) Isolation of DNA : DNA is isolated from the cells or tissues of body parts like blood, hair, skin, semen, saliva etc.


B) DNA amplification: If the obtained DNA quantity is small it is amplified i.e. subjected to in vitro replication by POCR (polymerase chain reaction) and obtain more copies of DNA.


C) DNA fragmentation
  1. The restriction endonuglease enzyme are used to cut the DNA at specific sites
  2. After the action of restriction endonuclease fragments of DNA are formed.
  3. These fragments of DNA are of variable length, the phenomenone is called as restriction fragment length polymor phism (RFLP)


D) Gel electrophoresis:
  1. The cut segments of DNA are then subjected to gel electrophoresis.
  2. Charge is applied the DNA which is negatively charged (phosphate backbone move to positive pole.
  3. Electric current sort or separate large and Small sized segments of DNA.
  4. The larger segments will go closer to the top and smaller to the bottom of the gel.
  5. This results in formation of bands


E) Southern blotting:
  1. A thin nylon membrane (nitrocellulose paper is let over the surface of gel and covered by paper towels.
  2. Paper towels will absorb the moisture from gel and DNA fragments will move to surtace of nylon membrane i.e. the single stranded DNA gets embedded into nylon membrane.


Hybridization:
  1. The radioactiveDNA probe are washed over the surface of nylon membrane.
  2. These radioactive probes will bind to complimentary DNA segment.
  3. It forms double stranded DNA structure; which remain embedded in the nylon membrane.
  4. The remaining single stranded DNA probe fragments are washed off.


G) Photography:
  1. This nylon membrane is kept in contact with X ray film.
  2. A pattern of think and thin dark band will produce on film due to exposure of radioactive labels (radioactive DNA probes.


Give the application of DNA fingerprinting?

Answer : Application of DNA fingerprinting:
  1. It is used in forensic medicine technique
  2. It is used to determine paternity disputes of child.
  3. It is used to settle insurance claims.
  4. It is also used in agricultural science, genomics.
  5. It is useful in study of phylogeny.

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