Sir /Ma'am...now I have given class 12 board exam;and now I am interested in Biotechnology in genetic engineering so how can I apply for it.
As you are from Maharashtra, the best option for you is IIT Bombay. It is one of the three IITs which offer Biotech courses. Other than this there are no class 1 option for this kind of course in Maharashtra.
IIT Madras and IIT Kanpur also offers courses in Biotechnology.
Some best institutes for genetic engineering in India are:
SRM University [B.Tech, M.Tech and PhD in Genetic Engineering]
Bharath University, Chennai [M.Tech in Genetic Engineering]
Aryabhatta Knowledge University, Patna [B.Tech and MTech in Genetic Engineering]
Hope it helps.