I am quite fond of the three molecular biology courses from MIT on edx [1][2][3]. Not only are the lectures great, but they also have spaced repetition built in. The exercises are often great counterfactual questions that encourage deep understanding.

[1] https://www.edx.org/course/molecular-biology-part-1-dna-repl...

[2] https://www.edx.org/course/molecular-biology-part-2-transcri...

[3] https://www.edx.org/course/molecular-biology-part-3-rna-proc...