RE: DNA. If you mix terms with real world scientific meaning into an explanation of magical phenomena, people get upset. Magic requires no explanation. Don't explain it. The whole idea is that it's "magic" and thus violates the laws of nature. Just state what the AU is. Your AU is that the biology is the same except that testosterone doesn't cause aggression and estrogen does. And it works because of Magic. That's it. Leave actual scientific terms out of it and we'll be OK.
Author's response
- Ahem. My world, my rules. I'll be ok regardless of how you feel about how my alternate universe works.