In humans at least, it is not the chromosomes, but the presence or abscence of genes for the production of testis-determining factor and mullerian inhibiting factor which determine sex. These genes are normally found on the Y chromosome, but sometimes they are damaged or absent. In which case you get a woman with XY chromosomes. -- SJK |
In humans at least, it is not the chromosomes, but the presence or abscence of genes for the production of testis-determining factor and mullerian inhibiting factor which determine sex. These genes are normally found on the Y chromosome, but sometimes they are damaged or absent. In which case you get a woman with XY chromosomes. -- SJK |
Some mention should be made of how this relates to the biological sexes as defined by role in reproduction and more generally by chromosomes (Y = male), which are very definitely discrete if not binary.
There are other sex chromosomes other than XX and XY, including XXX, XXY, etc. There are also some individuals who are mosaics -- i.e. some of their body cells are of one chromosomal sex, while others are of another. So chromosomal sex isn't a discrete dichotomy. -- SJK
The Y chromosome is dominant, so XXY counts as male while X and XXX count as female, at least with regards to the bulk of the anatomy, but I was already thinking of these when I said discrete if not binary. Mosaics are harder to categorize but they are pretty much inherently a mix of the two sexes, rather than a third sex separate from both (noone describes the truly hermaphroditic worms as having non-male-non-female sex). In any case, I think the distribution is sufficiently bimodal that emphasizing the continuity over the discreteness is a mistake. Evidently some people disagree, and in the spirit of NPOV I'm all for including what they have to say, but I'd include more details.
There is not one defintion of sex, but many -- chromosomal sex, internal anatomical sex, external anatomical sex, gender identity, social sex role, legal sex -- and although these different defintions most commonly coincide, they need not, and often don't. -- SJK
No way. For example in insects there are at least these systems: male XX/female XY, male XY/female XX, male X/female XX, male XX/female X and male haploid/female diploid. (X and Y are arbitrary sexual chromosomes, some of these combinations more frequent than others) There are more problems, because for many animals, sex is determined hormonally, not genetically, and can even change during adult live time.
In humans at least, it is not the chromosomes, but the presence or abscence of genes for the production of testis-determining factor and mullerian inhibiting factor which determine sex. These genes are normally found on the Y chromosome, but sometimes they are damaged or absent. In which case you get a woman with XY chromosomes. -- SJK