Muggle doctors cut people's arms off sometimes. My brother told me about this fellow who wasn't even very ill, but after a muggle doctor poked at him with dirty knives, he took a fever, and he'd have died if his leg wasn't cut off. It isn't their fault that they aren't any better at healing, but there's no excuse for not being clean.
Are you Mexican too? I'm afraid I don't know terribly much about Mexico, except that I read in the newspaper about that war over Texas, and I think that witches are called brujas there. I don't know what genetics is but I am talking about bloodlines and family and legacy.
You write rather well for your age! I'm fourteen. Are you here all by yourself, or is your abuela here too?