What is DNA fingerprinting? Describe various steps involved in the same.
- It is also known as DNA profiling/ DNA printing / DNA typing
- DNA fingerprinting was developed by Alec Jeffreys – british geneticists in 1984.
- According to this technique, the 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.
- 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.
- These sequence of base are called as minisatellite or VNTRs (variable number of tandem repeats).
- Each organism transmit such repeats to next generation which are used as genetic marker in personal identifing test.
Steps involve in making DNA fingerprinting:
- The restriction endonuglease enzyme are used to cut the DNA at specific sites
- After the action of restriction endonuclease fragments of DNA are formed.
- These fragments of DNA are of variable length, the phenomenone is called as restriction fragment length polymor phism (RFLP)
- The cut segments of DNA are then subjected to gel electrophoresis.
- Charge is applied the DNA which is negatively charged (phosphate backbone move to positive pole.
- Electric current sort or separate large and Small sized segments of DNA.
- The larger segments will go closer to the top and smaller to the bottom of the gel.
- This results in formation of bands
- A thin nylon membrane (nitrocellulose paper is let over the surface of gel and covered by paper towels.
- 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.
- The radioactiveDNA probe are washed over the surface of nylon membrane.
- These radioactive probes will bind to complimentary DNA segment.
- It forms double stranded DNA structure; which remain embedded in the nylon membrane.
- The remaining single stranded DNA probe fragments are washed off.
- This nylon membrane is kept in contact with X ray film.
- 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.
- It is used in forensic medicine technique
- It is used to determine paternity disputes of child.
- It is used to settle insurance claims.
- It is also used in agricultural science, genomics.
- It is useful in study of phylogeny.