Hello Santosh !!so..yah you can give GATE exam under CSE.But,it will be very difficult to you to manage with this cse core subjects ,which full of programming.And you need to work hard to get seat in good college,cut off is also high for this branch.Whatever be confident and do well.All the best for your exam!!
if you are a biotechnology student and you want to give GATE examination in CSE stream so you definitely can give it but it will be little bit difficult for you to prepare, because the entire syllabus and subjects will be new for you and you will have to do the same buckle down that a student do in the four year of BTech for CSE branch.
Best of luck.