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From: mmm@weitek.UUCP (Mark Thorson)
Newsgroups: net.bio
Subject: Human Genetics (a query)
Message-ID: <241@weitek.UUCP>
Date: Thu, 1-Aug-85 16:54:18 EDT
Article-I.D.: weitek.241
Posted: Thu Aug  1 16:54:18 1985
Date-Received: Sat, 3-Aug-85 08:42:56 EDT
Organization: Weitek Corp. Sunnyvale Ca.
Lines: 39
Keywords: sex chromosome recombination

I have a question about biology that some netter should be able to
answer:  Do human X and Y chromosomes recombine?

For non-experts, recombination is the process via which chromosomes
exchange material.  Humans have double sets of chromosomes; each cell
of your body (other than the sperm and ovum) has 46 chromosomes, half
from your mother and half from your father.  In the process of creating
the sperm and the ovum, a set of 23 is created.  The material in these
23 chromosomes is drawn randomly from your 46.

Without recombination, each of the 23 chromosomes would be identical
with one of the 46.  Hence your set of 46 would contain chromosomes
identical with chromosomes in your parents, grandparents, etc.  An
ancestor 10 generations back might make a significant contribution to
your genetics (one or two chromosomes) or no contribution at all (zero).

But this doesn't happen.  Each of the 23 (or at least 22 of them?) has
material drawn from both parental chromosomes.  Just before the 23
chromosome sets are formed, the chromosomes pair off and swap material
(recombination).  Thus you are likely to have small bits of DNA from
all your ancestors 10 generations back.  You may have a greater or lesser
amount from each, but you are unlikely to have none and unlikely to have a
whole chromosome.

But do the sex chromosomes recombine?  If they do, this has implications for
human sexuality in that sex cannot be contained in the whole chromosome
otherwise recombination would render most of the human population andro-
genous (maybe it does?).  Sex would have to (?) be contained at one site
so it would be resistant to splitting via recombination.

If they don't, this has implications for sociobiology.  It means that all
46 of a woman's chromosomes and 45 of a man's chromosomes are some genetic
hodgepodge of all his/her ancestors, but that a man's Y chromosome is
identical with his father's, paternal grandfather's, etc.  This is relevant
to the preponderance of patriarchal societies, the low status of women, etc.

Sociobiologically yours,

Mark Thorson (...!cae780!weitek!mmm)