This is all wrong: the parents start out with only 2 million base pairs of their genome ( 3 billion base pairs) different from each other. Although 1/2 your genes come from each parent 99.933 % of those genes are identical 2 x 10^6 / 3 x 10^9 = .00067 = .067%. That's why we all, save a very few, have 2 arms, 2 legs, 7 cervical vertebrae, etc. are are defined as a species. If parents had only 1/2 their genes in common they would be life forms at all, or at least one of them wouldn't.