Mostly. Triple X females have no symptoms, and don’t seem to have any problems from the extra chromosome. XYY men are usually very tall, and it was theorized for a while that they had violent tendencies, based on what seemed to be over representation among men incarcerated for violent crimes, but it turned out that the problem was poor sampling in the non-incarcerated group.
XYX men have something called Kleinfelter’s syndrome, and they do have problems. Sometimes they are sterile, and sometimes they develop gynecomastia. They have higher rates of learning disabilities than men without a second X chromosome, but they usually do pretty well, and life full lives. Women with a single X have Turner’s syndrome. They have late onset menarche, and occasionally are sterile. They have very short stature, although not short enough for it to be considered a form of dwarfism. They usually have a hearing impairment that is significant. They also have a problem with their necks being stiff, so they have to turn their whole upper body to look at someone to their side. I have read that they often have MMR, but everyone I knew with it, I knew from Gallaudet, so they were not only intellectually normal, but probably a little bit above to get into college. I have no idea whether Turner’s presents differently if the X is from the mother, or from the father.
If a blastocyst is conceived with just a single Y chromosome, it isn’t viable, and if it makes it to the implant stage, so the woman actually becomes pregnant, she usually loses the pregnancy before she even knows she’s pregnant.
Yes, I know. I have a PhD in Biology, and I spent the last seven years studying chromosome behavior in meiosis. That’s why I said sex chromosome aneuploidies are “survivable”. I didn’t say they were normal and healthy.
Well, then that post isn’t for you. Let other people who didn’t know that read it and go on.
Like I posted above, a single Y with no X is non-viable.
BTW, Smeg, since you study this, even if this isn’t directly on your topic, do you know if Turner’s syndrome manifests differently depending on whether the X came from the mother or the father?
BTW: if anyone wants an example of a genetic disorder that is caused by exactly the same gene, but manifests completely differently depending upon whether the defective gene come on a chromosome inherited from the mother, or the father, Prader-Willi syndrome and Angelman syndrome is an example. They both map to the same deletion on chromosome 15, but PWS results if the chromosome is from the father, and AS results if the syndrome is from the mother.
What is the mechanism for that? I wasn’t aware that chromosomes had any “memory” of which parent they came from. I guess there’s some form of epigenetic marking that goes on in the sperm and/or egg? How many generations can it go back-- Can a chromosome “remember” if it came from a grandmother or a grandfather? And what if there’s crossover?
Genetic imprinting. I believe it’s mostly a mammalian thing. The chromosomes we inherit are marked with patterns of CpG methylation that differ between our paternal and maternal chromosomes. It only goes back a generation - all of the chromosomes I give to my kids will be marked “paternal” regardless of where I got them. Some genes, for reasons that aren’t well understood, will only be expressed from either the paternal or maternal copy. Prader-Willi and Angelman syndromes are caused by all copies of a specific locus only carrying one methylation pattern.
As a side note, this is also an obstacle to one day figuring out how to use genetic material from same-sex couples to make children.
I was just curious because it seems to have variable expressiveness-- some women show MR and learning disorders, while others are cognitively normal, and some have ataxia, while others, aside from the stiff neck (I’ve seen it called “webbed”) appear to have normal motor control. I suppose any chromosome deletion disorder operates like an autosomal dominant disorder, and those often have variable expression. I know a guy who had such a mild expression of Noonan’s syndrome, he had no idea he had it until his son was born with a much more serious case.
So, what happens if all of the chromosomes have the paternal methylation patterns, or if they all have the maternal ones? Does that lead to any sort of disorders?
In any event, there’s certainly some means of changing the patterns, given that they get re-marked every generation.
Off the top of my head, I would suspect that variation would have more to do with whatever variants are present on the X chromosome rather than what parent it came from. Maybe. I’m going to stop thinking there before my brain brings up all of the objections to that statement I can feel lurking.
Yes. Big-time disorders. That’s essentially what happens with P-W and Angelmans, and that’s when only one small locus is affected. It’s called “uniparental disomy” - both copies of the locus come from one parent. It happens sometimes when you get weird DNA repair via recombination, or translocations, or stuff like that. I would be surprised if having uniparental disomy across the whole genome wasn’t fatal. In fact, there was a paper released a few months back showing that the number of genetic loci that are sensitive to imprinting was much higher than we thought it was. In the hundreds, perhaps?
The imprinting happens in germline cells. That’s where, as I make sperm, my DNA is all marked with my “paternal” pattern and my mom’s maternal pattern is lost. I would assume it’s done during S phase, but I’m not positive about the details.