I'd actually argue that all you really need is a Biology 12 or 1st year University level Biology to understand and explain it.
However Biology is so complex that unless you've been refreshing along the way, most people have forgotten what they do know (even if what they know is wrong). I guess it's similar in Physics and Chemistry (lots of details that one forgets).
This is why on the internet, you see pictures of photosynthesis (cycle diagram) and people excitedly scream "Krebs Cycle!" (It's the Calvin Cycle.) Because they kinda remembered it from HS when they had to memorize how much ATP gets created in the cycle (including in the electron transport chain), but forgot it's cellular respiration.
So for anyone trying to explain why transfections (asking your cells to express a foreign protein through an inserted mRNA strand) is bad, they must remember the mechanics of protein synthesis as well as the idea/fact that proteins get presented on the surface for inspection. Then they have to tie this into "common knowledge". For example, why are immunosuppressants used for organ transplant patients?
Basically walk from the top and explain it until it's at the level they no longer comprehend. The difficulty actually lies with people in a field where they should understand this. The show the greatest amount of cognitive dissonance in my experience. Yet even then, you can get them thinking if it's in an area they haven't had training against (e.g. IgG's trying to cross the blood lung barrier, why it's not transudation and why the mucosal layer orientation is the most important). Once you have a crack, you can approach them again later.
Also, the closer they are to you, the less likely they are to listen to you. It's an extremely weird human trait.