Anyone find it interesting all the mutants so far have been human ----> animal?

[Kidatheart]

Well, technically Bradford and Xavier would have had two foreign DNA on/in them when exposed to the mutagen.
Bradford's bite would contain the dogs DNA until his body starts to heal the wound and destroyed the invading parasites from the dogs mouth.
Xavier would have the fishes DNA in him until he breaks the fish down and expels it from his body.
So, depending on timeframe, what should have happened being exposed to basically two separate DNA, one from turtle, one from dog/fish? Should they have been mutated like they are, but with turtle shells on their back? Or does the exposure that has more DNA transfer "win" the battle for rights of the mutation?
If this is the case, then it doesn't have to be exactly the last foreign DNA that it the exposed mutagenated creature is mutated with.

[miru]

Cockroach Terminator used to be a normal animal. He was a mindless monster.