Is a student with a Bachelor's degree in Botany eligible for MS-PhD Biotechnology programme in IISc Bangalore even if he/she does not have mathematics in class 12?
Yes you are, perhaps you need to qualify JAM or GATE Exam in Biotechnology followed by Interview for admission in MS-PhD Programme in Biotechnology of IISc Bangalore.
As far as your 12th is concerned, there is no such criteria of having Mathematics, but you must have a First Class degree in either of Physics/ Chemistry/ Biological Sciences during Undergraduate Study.