What is a plasmid and How is it used in genetic engineering?

wow. just wow. Have you heard of wikipedia.org???

Plasmid is an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA. most of scientist use plasmid as a vector to transform new gene into bacterial host. You'll more about this if you learn  Recombinant DNA Technology..

PEACE =D

plasmids are small fragments of DNA with some inherant property.......eg in bacteria it can confer antibiotic resistance......in genetic engineering they use it in the blastocyst of the mouse cells before it grows into a foetus and develops into a mouse.......this sort of genetic eng will deduce the function of important genes after the eng........whether its important for functioning and survival......if the mouse dies....it indicates to us that that part of the gene has some important function with living........

etc.....many other areas of genetic eng........cell based tharapies coupling it to viruses to infect humans for therapy eg in cancer treatments......