User blog comment:WayfinderOwl/Questions about sims children/@comment-1441666-20130122181638/@comment-1441666-20130122183000

One more thing which I think will be relevant to you - after a couple of generations dominant genes become more interesting because a Sim born in game will take one gene from each parent, one of which will be displayed through their hair or eye colour and one of which is basically hidden, but still present. So, for example, the children you mentioned in your first question would have brown hair but would also carry a hidden recessive gene, in this case just for brown hair again, which would have little impact. But while their eye colour genes were brown (dominant) and their eyes would appear brown they would have a recessive gene for green eyes basically hidden in their DNA/coding. They will pass on one set of eye colour genes to their offspring and there is always a 50/50 chance as to whether the displayed/dominant or hidden/recessive gene is the one that gets passed on, so there would be a 50/50 chance that the gene they passed on to their offspring would be for green eyes like their mother's, even though their own eyes were brown like their father's. Then, if they were to have a child with someone who had, say, light blue eyes (another recessive gene), there would be a 50/50 chance that those children would inherit green eyes from their grandmother that way. This, I think, accounts for those cases when recessive genes display over dominant genes without the game glitching. I hope I explained that OK - science isn't really my thing in The Sims any more than in real life. :P