DNA fingerprinting technique | Molecular genetics | class 12 | Neet biology

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Molecular Genetics
In this video
✔️ Class: 12
✔️ Subject: Bio-Zoology
✔️ Chapter: Molecular Genetics
✔️ Topic Name: DNA fingerprinting technique
🧬The Steps in DNA Fingerprinting technique.
1. Extraction of DNA
The process of DNA fingerprinting starts
with obtaining a sample of DNA from blood, semen, vaginal fluids, hair roots, teeth, bones, etc.,

2. Polymerase chain reaction (PCR)

In many situations, there is only a small amount of DNA available for DNA fingerprinting. If needed many copies of the DNA can be produced by PCR
(DNA amplification).

3. Fragmenting DNA

DNA is treated with restriction enzymes which cut the DNA into smaller fragments at specific sites.
4. Separation of DNA by electrophoresis

During electrophoresis in an agarose gel, the DNA fragments are separated into bands of different sizes. The bands of separated DNA are sieved out of the gel using a nylon membrane (treated with chemicals that allow for it to break the hydrogen bonds of DNA so there are single strands).

5. Denaturing DNA

The DNA on gels is denatured by using alkaline chemicals or by heating.

6. Blotting

The DNA band pattern in the gel is transferred to a thin nylon membrane placed over the ‘size fractionated DNA strand’ by Southern blotting.

7. Using probes to identify specific DNA

A radioactive probe (DNA labeled with a radioactive substance) is added to the DNA bands. The probe attaches by base pairing to those restriction fragments that are complementary to its sequence. The probes can also be prepared by using either ‘fluorescent substance’ or ‘radioactive isotopes’.

8. Hybridization with probe

After the probe hybridizes and the excess probe washed off, a photographic film is placed on the membrane containing ‘DNA hybrids’.

9. Exposure on film to make a genetic/DNA
Fingerprint

The radioactive label exposes the film to form an image (image of bands) corresponding to specific DNA bands. The thick and thin dark bands form a pattern of bars which constitutes a genetic fingerprint.