You can sure as hell bet that I'd take that crack at my education and intelligence as an insult, what else could it be?
So you wanna refute my scientific knowledge, kiddo? Let's see. 4 years of high school science, 3 courses while at college, and three years of biology, including college courses DURING high school. And there's going to be a hell of a lot more in my future, bio in particular, as science is my favorite subject and is relevant to what I'm studying.
Put short? When I'm talking scientific stuff, I know my shit.
If you were to put a piece of celery into a blender and turn it to mush, would it not be celery anymore because the shape is different? No, because it would still consist of the same cells and contain the same genetic material. If you were to put a carrot and piece of celery in a blender together and turn THAT into mush, would the resuling goo be something new? No, it would simply be celery mush and carrot mush together, as it would be the same as before - celery cells and carrot cells that contain the respective genetic material.
So long as the original cells are still there, it still contains the original genetic material and thus as a result still biologically whatever it was when it started out.
Physiology is determined by genetics. But physiology changing does NOT mean the genes themselves, or cells carrying these genes, change. That's simply ridiculous and I can't imagine anyone who's taken any sort of basic science class thinking that.
As for the Master's body-hopping? Most logical and simplest answer would be that he implanted some of his genetic material into the host. For all we know this could be some ability that Time Lords have that we don't know about.
And Time Lord is a race, not an attribute. It's as I said - you are one or you aren't.