hello,

see biotechnology gate papers has two sections, aptitude

the and engineering mathematics are common section wheres you have to choose your stream and study accordingly. kindly follow the below link to go through gate biotechnology syllabus:

https://cache.careers360.mobi/media/uploads/froala_editor/files/BT_Uor9fzY.pdf

first of all I suggest you to follow your text books for the basic conception clearance. after that you may solve papers from  10 years gate solved books.

engineering maths by bs grewal

quantitive aptitude by rs agarwal

GATE Tutor- Biotechnology by Arihant Publications