Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site cylixd.UUCP Path: utzoo!linus!philabs!prls!amdimage!amdcad!decwrl!decvax!harpo!whuxlm!akgua!akgub!cylixd!charli From: charli@cylixd.UUCP (Charli Phillips) Newsgroups: net.bio Subject: Re: Human Genetics (a query) Message-ID: <186@cylixd.UUCP> Date: Thu, 8-Aug-85 20:59:12 EDT Article-I.D.: cylixd.186 Posted: Thu Aug 8 20:59:12 1985 Date-Received: Mon, 12-Aug-85 07:15:56 EDT References: <241@weitek.UUCP> <1775@reed.UUCP> Reply-To: charli@cylixd.UUCP (Charli Phillips) Organization: RCA-Cylix Communications Network Inc., Memphis, Tn. Lines: 23 In article <241@weitek.UUCP> mmm@weitek.UUCP (Mark Thorson) writes: > I have a question about biology that some netter should be able to > answer: Do human X and Y chromosomes recombine? and > But do the sex chromosomes recombine? If they do, [...] > Sex would have to (?) be contained at one site > so it would be resistant to splitting via recombination. If I remember correctly from the Human Medical Genetic course I took in college some years ago, the only known function of the Y chromosome was to "turn on" the production of androgen at an early stage of pre-natal development. All fetuses develop as females before that point, and those with a Y chromosome "become" males as a result of the effects of the androgen. Because some XY fetuses are insensitive to the effects of androgen, it is possible for a genotypic male to be a phenotypic female in every respect, including reproductive ability. (Such XY women are typically infertile but not sterile, since their "Y" eggs are useless.) Recombination of genes across the X and Y chromosomes probably occurs for those few genes that are on the Y chromosome, but it is an extremely small gene and seems to carry very little information.