throopw@sheol.UUCP (Wayne Throop) (06/17/91)
- doug@netcom.COM (Doug Merritt) = lsj@quark.lu.se (Sverker Johansson) writes = Any gene sitting on the Y chromosome is only possessed by males = (apart from whatever genes may be _both_ on X and Y). - Right; there are genes that are on both, and there are those that are - unique to one or the other. There are periodic reports of new research - uncovering examples of each of those three categories. Hmmmmm. The books I consulted on this subject weren't crystal clear. _Human_Chromosomes:_Structure,_Behavior,_Effects_, Eva Therman, 1986 had the most clear statement, and even it doesn't give me a definitive answer to the burning question: what percentage of genes on the sex chromosomes recombine during meiosis. I had been thinking that it was as near 100% as made no difference. Certainly the simpler books I had on hand implied this, though didn't say so outright. "Human Chromosomes" says (near as I can make out) maybe 75%, maybe much less. But it seems very unlikely to be the case that *any* gene sitting on on a Y can only be passed on to males. Anyhow, with a significant nonrecombinant fraction, the more males the merrier. But keep in mind that any genes which don't recombine would have single descent, and as a matter of statistics would tend to become dominated by one particular forebear or another over many tens of generations. - It's unclear to me whether Wayne's point about the relative unimportance - of this is true or not Well... it's not *clear* to me, either. It just didn't seem that 50/50 males/females in an adam/eve scenario gave any particularly important and clear-cut benefit. I guess I still don't know enough to say either way. I'm crossposting this to sci.bio with followup back to rec.arts.sf-lovers. If anybody can refer me to straightforward information on how much recombination goes on between X and Y during meiosis, in either humans in particular or mammals in general, I'd be obliged if you'd email me. -- Wayne Throop ...!mcnc!dg-rtp!sheol!throopw