Mouth would be the most and if you constantly wash your hands it’d be your hands
Hope this helps
My answer -
It affects an animal's adaption
Natural selection might take place. In order for the adaption to occur.
P.s
Happy to help you have an AWESOME!! day
Because each gamete has only half the amount of DNA of a normal cell, when the male and female gamete unite, the zygote has a complete set of DNA.