From kragen@dnaco.net Fri Aug 21 10:44:16 1998 Date: Fri, 21 Aug 1998 10:44:15 -0400 (EDT) From: Kragen To: systalk@ml.org Subject: Re: [ST] AH HA! In-Reply-To: <35D4DCC2.9A6CD77D@ifl.edu> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Keywords: X-UID: 1313 Status: O X-Status: On Sat, 15 Aug 1998, Storck Marc wrote: > Joshua E. Rodd wrote: > > (Incidentally, if I had children, 1 out of 4 would have the effect > > passed > > on. If I married someone who also had the disease, then all the children > > would have the effect. Does that mean we would all be nice looking? =) > > So your disease is on the X-chromosom and it is no dominant, that's the only > possibility for a 1 of 4 If it were sex-linked, on the X-chromosome, and not dominant, then it would explain his second comment -- that marrying someone who also expressed the trait would result in all the children expressing the trait -- but not the first, because either no children would expressing the trait (if he married someone who didn't have the gene at all), or half of the children of both sexes would (if he married someone who had the gene.) If it were not sex-linked and not dominant, then either none of his children (with a partner without the gene) or one-fourth of them (with a partner who had the gene, but didn't express it) would express the trait if his partner did not express the trait, and (again) all of his children would express the trait if his partner also expressed the trait. If it were sex-linked and on the Y chromosome, it would never be expressed in women, so it would be impossible for him to marry someone who also had the disease, but no matter who he married, all of his sons would express the trait. (Y-chromosome traits are neither dominant nor recessive under normal circumstances, since only XYY-syndrome sufferers (about 1 in 2000 people) have two different Y chromosomes.) If it were sex-linked, on the X chromosome, and dominant, then it would be expressed in none of his sons (unless they got it from their mother) but all of his daughters. If it were not sex-linked, but were dominant, then there would be two possibilities for his genotype and three for his mate's, which would mean six total possibilities: if either Joshua or his wife had it on both genes, then all of their children would express the trait (which covers four of the six possibilities); if they both had it on one gene (which would mean they both expressed it) then three-fourths of their children would express the trait; if Joshua had it on one gene, but his wife had it on neither gene, than half of their children would express the trait. In short, none of the scenarios match what Joshua said -- unless he plans to have children with lots of different mothers, which I doubt. Kragen