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vovan
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Well, I was reading this here thread:
Why are gay marriages legal but not polygamist ones?
And here is what I'm thinking. It is pretty clear that gay marriages will be allowed eventually. Now, gay couples will probably want to have children. At first they will adopt them. But then suppose human cloning is allowed, which isn't all that impossible. Now, it is already possible to make a clone of an animal using the DNA from a non-sexual cell. In other words, you can extract it from a blood cell or what not, and fertilize the egg, and it would work.
So, now, the gay couples would probably want to have children "of their own", meaning, those that have parts of the genome of their parents. That would be quite possible if the cloning of humans is allowed. Would work fine and dandy, too: take half the genome of one guy, half the genome of the other, hire a woman to carry the baby (or raise it in a lab), and voila, you have a baby that's really the child of the gay couple: it has their genes.
Now here is the question: suppose the sets of chromosomes taken from both guys contain a Y-chromosome. What will happen then, theoretically speaking? Will the embryo even start developing? Of course, there is no predictinig what the result would be if it does... But will it develop, or will it just stop at a certain stage?
Don't know if there are any biologists visiting 'Poly, but I am curious nonetheless. 
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vovan
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Well, I am not really talking about the time constraints for that. I mean, eventually, the technology of cloning will evolve to the level that that would work.
For now, yes, you can only insert foreign genome into the egg, but not the sperm.
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vovan
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Well, that's what I'm thinking too, it wouldn't work. Since naturally, the embryo dies eventually if it has some bad genetic disorder. But naturally, that can't happen: for an embryo to have two y-chromosomes. So, from an evolutionary stand-point, since nature has never been challenged with such a disorder, chances are, there is no defense mechanism against it.
Speaking more scientifically, I guess, the determining factor would be the role of the chromosome in the development of an embryo. Obviously, it determines the shape of sexual organs, through the production of horomones. But what other uses do these hormones have? After all, if the genome in that X or Y chromosome does not determine any vital characteristics, chances are the embryo would, in fact survive.
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vovan
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quote:
Originally posted by Frogger
IIRC there are some people who have a genetic abnormality where they receive two Ys and an X, though... |
IIRC, that's two X's and a Y... That's when the egg or the spermatosoid does not divide properly initially, and has the full set of chromosomes instead of a half.
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vovan
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quote:
Originally posted by DeathByTheSword
they tried such a experiment in 'old russia' I think.
well atleast they tried and the result was a 'thing' that was not fit for life |
They might have tried, I don't know, though I seriously doubt it, but surely the technology was pretty weak to accomplish real cloning, any way, not speaking of creating something impossible.
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CerberusIV
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I did a bit of this in a biology course a few years ago. If you are male you get an X and a Y chromosome, if female two X's. Sometimes the chromosomes don't divide properly and someone gets more than one X chromosome. This is not a fatal problem as the extra X just curls up into a ball and doesn't do anything. Known as a Barr body IIRC. People with this condition are susceptible to some disorders but it is certainly not fatal.
It is theoretically possible to take an egg, kill the DNA, insert an X chromosome from one guy (probably from an X sperm since that has already divided) and a Y chromosome from the other guy and have a male child. Or use two X's and get a girl. A lesbian couple could only have a girl. A female volunteer to carry the implanted egg would also be required.
Something very similar has been done with cells from toads but 99% died and only 1% turned into viable adult toads. So we are a long way from this sort of thing in humans but it may not be impossible one day. Like most things it can probably be done if someone wants to try hard enough and throw enough money at it.
If it can be done I am not sure I would be happy with the ethics though, the science is outrunning the ethics as it is and whether we should needs a lot more thought.
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vovan
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quote:
Originally posted by CerberusIV
Sometimes the chromosomes don't divide properly and someone gets more than one X chromosome. This is not a fatal problem as the extra X just curls up into a ball and doesn't do anything. Known as a Barr body IIRC. |
You are correct. In women, only one of the two X-chromosomes is active and actually determines the phenotype. The other one turns into a Barr body - an inactive bunch of DNA. Thus, a normal woman would have only one Barr body, but if she has more than two X-chromosomes, which happens every once in a while, there would be just be more Barr bodies, that's all. Same for males with more than one X chromosome. They remain male, but the extra X chromosomes are not active.
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vovan
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quote:
Originally posted by Urban Ranger
You sure? |
Yes.
quote:
Human females inherit two copies of every gene on the X chromosome, whereas males inherit only one. <...> Are males at a disadvantage in the amount of gene product their cells produce? The answer is no, because females have only a single active X chromosome in each cell.
<...>
The cells of females have only one functioning copy of each X-linked gene - the same as males.
X-inactivation occurs early in embryonic development. In a given cell, which of a female's X chromosomes becomes inactivated and converted into a Barr body is a matter of chance (except in marsupials like the kangaroo, where it is always the father's X chromosome that is inactivated). After inactivation has occurred, all the descendants of that cell will have the same chromosome inactivated.
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Source
However, in some animals (and I think in humans too, but I am not sure) the different cells of a female can have different X-chromosomes deactivated. That's the way, for example, they explain tri-color cats. These are the cats that have patches of three different colours: white, brown, and black. Only females have those: males can only be unicolored or bi-colored, unless, that is, due to genetic defect they get multiple X-chromosomes. And that is because different parts of the female's skin can have different X-chromosomes inactive. Thus, some parts would be black, and others - brown. A simplified but more detailed explanation of how that works can be found here:
http://www.fanciers.com/cat-faqs/tricolors.shtml
Last edited by vovan on 18-03-2003 at 08:15
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vovan
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quote:
Originally posted by Urban Ranger
You can always go for something like XXXX or XXXY. That will work theoretically. |
Yes, and that happens in real life, too. Like I explained in the above post (and in the source of that quote, you can actually find more on that multiple X chromosomes, on the bottom of the page), the extra X-chromosomes just get deactivated and turn into Barr bodies.
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vovan
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quote:
Originally posted by Urban Ranger
It appears that it is not necessary for for all the genes on the Barr body to not be expressed. |
Yeah, that's the odd part...
But I think you are right in that an embryo with only Y chromosomes wouldn't be functional. After all, we know that such disorders as colour-blindness, hemophilia (is that what it's called when the blood does not clog?), and some others are related to genetic disorders of the X-chromosome. Thus, it does contain genes that code for some important stuff - related to blood and vision, at least.
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18-03-2003 02:12
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