If you start at a broad source like Kahn Academy or wikipedia, leave it at that: a start! Use what you learn there to refine your search in proquest, jstor, and other databases and websites.
Search for your terms in quotations to search as a phrase, adding keywords you're interested in: i.e. "genetic transformation" agriculture or "gene regulation" cancer
You will find scholarly journal articles (a.k.a. peer reviewed articles) on these topics. These articles can be long and are written for a specific expert audience. they can be 20-30 pages. Fret not! You can glean enough information by reading the abstract and introduction. If you are still intrigued or want more from the article, read the conclusion (if there is one) and then skim the article paying special attention to the topic headings and graphs or other visuals and their captions.