About 3 weeks ago my daughter-in-laws younger sister had to be hospitalized for some difficulties involving a disorder that she has called Prater-Willi (sp?) Syndrome. It is a congenital problem that has left her very slow mentally and with a voracious appetite. It is caused by an erased 15th chromosome.
What amazes me is how much incapacitation that small chromosome has caused. On the other hand, she is a very loving, caring, capable human being.
I think the math of genetic make-up will demonstrate that the combinations, permutations, and expressions of such genetic things goes far beyond a mere number count of genes.