I would suggest taking MIT's Secret of Life course on EdX. Its taught by Eric Lander who was a key figure in the human genome project and was a mathematician beforehand, so he follows an axiomatic approach that is much different than the way other schools teach biology
Alternatively, Harvard Extension School has some great biology courses you can sign up and get credit for. Though those are mostly for pre-med career changers
https://www.edx.org/course/introduction-to-biology-the-secre...
Alternatively, Harvard Extension School has some great biology courses you can sign up and get credit for. Though those are mostly for pre-med career changers