A normal human female carries the chromosome pair XX, and the male carries XY. XXY and XYY exist as abnormalities that give rise to known characteristics. Has there ever been a case of YY, and if so was it viable and what were the characteristics? [Question arising out of some complicated genetic work I've been involved with - fictionally, of course...]

Jafato

No, it is impossible to produce a viable human that is lacking an X chromosome, as in a yy individual. There are several genes on the X chromosome that cause disease when deleted, such as the genes for Haemophilia, Menkes syndrome, familial Leukodystrophy, and several others genes that are homozygous lethal, i.e. at least one copy is required for the person to survive. An embryo without any X chromosomes would not have any copies of any of these genes, and would die early in development. http://www.madsci.org/posts/archives/1997-03/859409178.Ge.r.html Feb 25 08, 4:40 PM

Flynn_17

YY would not be a viable chromosome configuration as the Y chromosome carries very little in the way of genetic material. It is, however, possible for someone to have a single X chromosome (this is known as Turner's syndrome), and for a human to have XXX (which is annoyingly known as Triplo-X, not exactly descriptive.) The reason that YY is not viable is that the Y chromosome does not contain anywhere near a full compliment of genetic material, and while it is possible for a human to inherit two Y chromosomes, it is, as you say, in subjects who are XYY, XXYY, etc. While X chromosomes have little to do with the definition of gender, they do contain the genes that code to create nearly everything a human needs to live. Feb 25 08, 4:44 PM

Baloo55th

Another Wow! to both. This was just out of curiosity as I was transferring chromosomes between eggs after splitting them... I had a feeling that YY would be lethal. (I've known a Turner's Syndrome case but not knowingly any of the others.) Thanks, folks. Feb 25 08, 4:53 PM