[SunilNagpal]

Hello Kunal,

Request you to refer the previously posted threads at:

http://in.biotechstudents.com/gate-biote...cts-books/
http://in.biotechstudents.com/unknown-fa...e-biotech/
http://www.biotechnologyforums.com/thread-2174.html
http://www.biotechnologyforums.com/thread-2329.html
http://in.biotechstudents.com/gatebt-crucial-topics/

And yes you can crack the exam in 6 months (that's more than sufficient time, in-fact). Focus more on being conceptually clear for the important topics of the syllabus (use google/youtube/McGraw animations etc for getting in-depth knowledge of the concepts you aren't clear about). Go through the previous year papers (in depth, exploring every option).
Clearing GATE is more about keeping calm and making best use of your existing knowledge, than being an 'extra-ordinary' student (because in my view, everyone is alike. anyone can clear GATE). Those who handle their nerves well, go through the exam easily.