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!