DNA Fingerprinting involves different stages - 1. First is isolation of DNA from target cell. 2. Then treatment of restriction digestion of DNA to generate DNA fragments. 3. Then separation of DNA fragments using Agarose Gel Electrophoresis . 4. Transfer of Agarose Gel DNA bands to nitrocellulose membrane filter. This filter paper after the DNA transfer is known as Southern Blot . 5. Then use of complementary DNA Probe to bind with target DNA . 6. X- Ray film exposure which represent Dark bands of DNA called DNA Fingerprints .

1. Biology – let’s simplify

2. DNA FINGERPRINTING
STEP-1. DNA EXTRACTION : BLOOD
SEMEN
CHEEK
SWABS
CHEMICAL
TREATMENT
PURE
DNA

3. STEP- 2. PCR
Amplification of the sample.

4. CUTTING : RESTRICTION ENZYMES
Molecular ‘scissors’ : Cut the DNA at specific
site to isolate the VNTRs.
E.g.- EcoRI cuts at 5’…GAATTC…3’

5. SORTING : GEL ELECTROPHORESIS
• Agarose : Linear polymer extracted
from seaweed.
• Migration of DNA in Agarose Gel
dependent on four factors :-
• Molecular size of DNA
• Conformation of DNA
• Agarose concentration
• Applied current

6. GEL ELECTROPHORESIS STEPS
DNA is
negatively
charge
molecule.
Smallest DNA
Fragments
move fast.
Largest DNA
Fragments
move slowly.

7. SOUTHERN BLOTTING
• DNA is ‘blotted’
out of the
Agarose gel on to
a piece of nylon
membrane by
Capillary action.
• ‘Unzipped’ to
produce single
strands of DNA.

8. PROBING : RADIOACTIVE DNA PROBE
• Nylon membrane is
incubated with radioactive
probes.
• Probes: Minisatellite DNA
tagged with radioactive
phosphorous.

9. Dna fingerprint : X-RAY FILM EXPOSURE
• Radioactive DNA bands
visualized by exposing the nylon
membrane to X-ray film.
• When exposed to radioactivity a
pattern of more than 30 dark
bands appeared on the film.