this is commonly know for the change in a single pair of genes or chromosomes that alters the host in many ways, dealing from areas like the reproduction organs, to the brain itself.
this could also change the way and organism looks, the color hair, eyes, skin tone. or even how they act or there inherited genes, being shy, open, or hateful. mutations can be both bad and good but in this case, we are talking about good mutations that really have no major affect on the hosts body.