Question

can any body tell me that how DNA of any person is checked??

Answer 1

Quite simple, did it in my first year, you need to separate out the DNA from the cells, so you take a sample and begin several steps to isolate and purify. Sample=eg Blood
1) Isolation of Leucocytes; leucocytes separated from the RBC's(red blood cells) in a hypertonic solution and centrifuge the sample to a pellet. the supernatant contains the lysed RBC's. We take out the pellet
2)Lysis of Leucocytes; SDS(a detergent) disrupts the cell membrane.
3) Removal of Contaminants & Protein; We use 'Salting Out' procedure which forms a precipitate with the contaminants due to its negative charge and positive charge of the salt. The precipitate is removed through centrifuge
4)Recovery of Intact DNA; We precipitate it out of solution using Isopropanol and centrifuge it to form a DNA pellet and carefully remove the supernatant
5) Washing DNA; washed with 70% ethanol to remove further contaminants which are soluble in the ethanol. DNA is not soluble therefore remains intact.
6)DNA Re-suspension;we resuspend it in a small volume of Tris EDTA (TE) buffer to stop the DNA being degraded.

All the chemicals used have purpose and help stop enzymes degrading the DNA but thats a whole other paragraph to write. basically everything has EDTA in it which absorbs calcium which the enzymes neet to degrade DNA.
Ok to actually check the DNA, we run it out through agrose gel electrophoresis which pulls the DNA out depending on weight.
Here is one i wrote earlier, its good information; http://en.wikipedia.org/wiki/Gel_electrophoresis