[michel_mr (OP)]

hello every one ,i have a lecture about detection of genetic polymorphism and i want to know the role of the restriction enzyme concerning this subject,i know many things about them like they r naturally produced by bacteria and used to cut the DNA molecules ....so any one can help

hello all

[chris]

Restriction enzymes are also called restriction endonucleases. They cut nucleic acid chains in the middle of the chain rather than at the end (hence endonuclease as opposed to exonuclease), and are referred to as 'restriction' endonucleases because they 'restricted' to cutting only in certain places. This restriction is determined by the genetic sequence.

For instance, the restriction enzyme Eco RI cuts (at the place marked ^) whenever it sees the DNA sequence G^AATTC. If you digest an individual's DNA with one of these enzymes it will be chopped up into a number of fragments of different sizes, each with the restriction site at both ends.

But sometimes a person's DNA will carry a mutation (a change in the genetic material) which alters the DNA sequence at the restriction site so that a certain enzyme can no longer cut there. This means that one of the fragments produced will be a different size to a 'normal' person and can be used to highlight the presence of the mutation. This is referred to as restriction fragment length polymorphism (RFLP).

The best example of this technique at work is in pinpointing the mutation that causes sickle cell anaemia. By sheer fluke, the mutation that causes sickle cell anaemia (a condition in which red blood cells deform into a crescent shape under low oxygen conditions) involves swapping the DNA letter A for a T. This removes the restriction site for an enzyme called Mst II which normally looks for -C-C-T-N-<b>A</b>-G-G-. But in sickle patients their sequence reads -C-C-T-N-<b>T</b>-G-G-. (N = any DNA base)

This means that if you cut their DNA with Mst II you will generate a different sized fragment compared with a healthy person, helping you to make the diagnosis.

Dalya Rosner and I wrote and article last year all about DNA (Genetic) fingerprinting and RFLP analysis - this may help to provide you with a little more information:

http://www.thenakedscientists.com/HTML/articles/article/dalyacolumn8.htm

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[smart]

What is a endonuclease inhibitor, and could recombinant influenza vaccines introduces rna-guided gene drives into the genome of human populations; making antiobiotic resistance inefficient agaisn't pandemic viruses ?

http://www.rcsb.org/pdb/explore/explore.do?structureId=5DEB