I am bio student. I can work in isro.
Shivani,
Joining in ISRO totally depends on your PCM marks. It's necessary for you to have these subjects in your 12th board. It's okay if you have done biology with these 3 subjects. Only then you can join ISRO. The primary institute for joining in ISRO is IIST Thiruvananthapuram. They only consider PCM marks and conduct exam with these 3 subjects only. JEE advance rank is completely applicable for joining there.
Eligibility criteria for IIST exam:-
The candidates of GEN/ OBC should have an aggregate of at least minimum 70% in Physics, Chemistry and Mathematics in the qualifying examination.
The reserved category candidates should have the minimum percentage of 60% in PCM subject of the qualifying examination.
Hope this helps!