Geneticists: is YY a viable chromosomal pairing?

Okay, so most of humanity possesses XY (male) and XX (female) chromosomes. But some people are born with chromosomal abnormalities, resulting in XXY (Kleinfelter’s Syndrome), XYY (so-called “supermale” syndrome), and just one plain X (Turner’s Syndrome).

Okay, let’s suppose that a woman with Turner’s Syndome meets a “supermale” and they get down to business. Now, most women with Turner’s aren’t fertile but let’s assume this one is. The egg she releases is blank, lacking the X chromosome found in normal eggs. The sperm that fertilizes it is YY, carrying a double pairing of the male chromosomes from her XYY mate. Is this embryo viable? Or are the odds of a YY embryo occuring so unlikely that we just don’t know?

I don’t think it’s possible, from my biology classes (I got my final mark for Bio 30 (Gr12 bio) it’s a 96) the Y chromosone is just a small scrap of genetic information (that is why men are more suseptable to sex linked diseases, it is more likely that a recessive will show through on the X chromosome because there isn’t another chromosome present with a dominate gene to block out the effects of the recessive) so I don’t think that there would be enough genetic information for a fetus to develop at all; I’m sure the body would abort an YY pretty quickly.

Possession of at least one X-chromosome is essential for life. A YY zygote would be non-viable and quickly aborted.

Some organisms can have a supermale (YY), but not humans.

Nope. There’s a whole lot of important stuff on the X chromosome that you’d die without. If you did manage to get a YY fertilized egg, it’d die pretty quickly.

IIRC, around 10% of the genes in the genome are on the X. YY embryos never develop beyond the first few cleavages – in the mouse, gene transcription begins at the 2 cell stage and I can’t imagine they would survive much beyond that.

No, a YY is not viable. Neither is a “just Y”. You require at least one functioning X to supply certain critical information.

Women with Turner’s syndrome are never fertile - their ovaries never develop. You need two XX’s to get fertile eggs.

Too elaborate, in any case - your hypothetical scenario could happen with a woman releasing an egg that simply doesn’t have any X at all - just as likely, to my mind, as a sperm arriving without either an X or a Y. In which case the X-less egg meets a sperm with a YY (which must happen to get the occassional XYY we see).

In any case - the resulting zygote will not survive.

A lot of people have replied already, so I’ll just add my two cents.

Apparently there are some women with Turner’s Syndrome that are fertile. Cite. No, I had no idea either.

However, a YY zygote is not viable. The X chromosome is much larger than the Y chromosome and contains a much larger number of genes, which is why colour blindness, hemophilia and the like affects almost exclusively males (there’s no second X chromosome to block off the bad effects of the gene on the first X chromosome). Cite. In fact, the only genes on the Y chromosome have to do with male bits and male stuff (don’t you love this technical talk?), while there are a lot of things on the X chromosome that we really need.

Re: fertility in Turner’s syndrome:

That’s not what I meant by “fertility”. I specifically stated that women with Turner’s syndrome never develop functional ovaries, and thus can not produce eggs. Thus, they are infertile.

Saying an egg donation makes a woman “fertile” is like saying a man who lacks sperm becomes fertile if he buys sperm from a sperm bank. It’s a means of circumventing infertility, not really a cure. I actually was aware that women with Turner’s syndrome have given birth, but they are not genetically related to those children. (They are still ‘mothers’ in every other important sense of the word, however)

Just because I can’t resist:

“almost exclusively” is not never - there is at least on color-blind woman who frequents these boards.

There have also been a very few female hemophilliacs, now that the men are routinely living long enough to have children of their own. The girls do have a distressing tendency to hemorhage massively once a month when they hit puberty. I think early hysterectomies are recommended in these very rare instances.

Sure, you can get women who are afflicted with X-linked diseases. They just need two copies of the bad X chromosom. It’s rare, but it happens.

Notice, however, that the article said most, which implies that at least a few women with Turner’s Syndrome can conceive. Which brings me to my next question…

Since the YY pairing is nonviable, suppose instead that the blank egg is fertilized by an XY sperm instead of a YY. This would, I imagine, produce a normal male – but would he have any genetic relationship whatsoever to his “mother”? This sounds to me like an incredibly odd way to biologically clone oneself.

If nothing else the offspring would, as usual, inherit his mother’s mitochondrial DNA so he would have that genetic relationship with her.

XX uniparental disomy (inheritance of two X chromosomes from one parent) will cause massive developmental disorders by itself due to a complex genetic phenomenon called imprinting.

My impression is that even XY uniparental disomy will not survive or will show significant problems. I’ll do a lit search later on this weekend.

It says that “most” women with Turner’s Syndrome cannot conceive a child, implying that some can.

But even if the egg had no sex chromosome, and the sperm had an XY, and that embryo was viable, the resulting baby would still not be a clone of the father, since there are all the other 40-some non-sex chromosomes that the baby would get from the mother.

But the odds of a defective egg meeting a defective sperm and producing a viable baby are pretty low, much much lower than the chances of a single defective gamete meeting a normal gamete.

22, to be exact.

I don’t have a cite for this, but I suspect that those few cases aren’t “pure” Turner’s syndrome, but represent XX/XO chimeras (meaning that some of the cells in the person are XX and others are XO). Chimeric individuals are rare, but do occur, and an XX/XO chimera would show the phenotype of Turner’s syndrome (to a variable degree, depending on the percentage of the body’s cells that are XO) but might have some ovary development and thus be fertile.