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Esq.
06-03-2006, 10:36 AM
It has always been my understanding that the male determines the gender of a fetus (why it was dumb of Henry the VIII to divorce Catherine of Aragon for not producing a male hier) and that all eggs contain the X choromosome, and thus are female until made male by the sperm (which contributes either another X chromosome, making the fetus a female, or a Y chromosome, making the fetus male).

However, my SIL told me that that egg selects which sperm will fertilize it, and thus the woman determines the gender of the child. I googled this concept and came up with some spotty research. Does anyone know more about this?

MichelleRenee
06-03-2006, 10:37 AM
There are boy sperm and girl sperm. Whichever sperm gets to and penetrates the egg first determines the gender. I am not sure if the egg has the ability to "reject" sperm... I think just the strongest one that gets there first is the winner.

pacificbliss
06-03-2006, 10:40 AM
I remember a study came out showing the cervix contracting to pull sperm toward it. That was a big deal because it had been thought it was all up to the sperm to get there and this study showed the female reproductive organs played an active role. Maybe that's what your SIL was thinking of. Still, I believe the first sperm to the egg wins, it's a fairly random process which is why the chance of one sex over the other is about 50:50. It is true that all eggs are X and sperm are either X or Y. XX=female XY=male.

Sophia
06-03-2006, 11:02 AM
I think there have been studies that showed some women's body chemistry may favor x-sperms over y-sperms, or vice versa, but it seemed to be an imbalance, not a typical thing. I'd still go by the idea that the man determines sex because the sperm carries the gene that determines sex.

Ericka
06-03-2006, 01:47 PM
What I have read: The sex of a baby is determined by the two sex chromosomes inherited from the parents. A baby will normally inherit one sex chromosome from the mother, and one from the father. A woman has two X chromosomes, so she can give either of her X chromosomes. The father can give either his X or Y chromosome.

Since the egg already contains an X chromosome (from the mother), the gender of a baby is determined by the X or Y sex chromosome of the sperm cell from the father (thus adding one more thing to the "blame it on the husband" list if things don't go as planned).

A girl baby will result if the final arrangement is XX, and a boy will result if it is XY. As you would expect, about half of the sperm cells contain an X chromosome, and half contain a Y chromosome. It is possible to have an abnormal number of sex chromosomes, however, this is extremely rare. http://sheknows.com/about/look/12.htm

lawgirl4
06-03-2006, 04:21 PM
take a look at this thread:

http://www.constantchatter.com/showthread.php?t=18840

on page 3, soulmate said the following:

"Nope. The egg has an equal part in gender selection. The casing of the egg is at a certain pH level that will be more friendly towards either the X or the Y chromosome sperm depending on the egg that pops out. So one cycle the egg may be more willing to allow an X chromosome sperm in while during another cycle the egg would be more willing to allow a Y chromosome sperm in. So if a man is more X or Y dominant in their sperm...the woman's eggs would still have some influence. Maybe that has something to do with cases of unexplained fertility??"

I had never heard of that before, but it certainly sounds plausible, and interesting...

bunny nose
06-04-2006, 07:35 AM
This is what we were told when we went for genetic counseling:

Both men and women have 23 chromosomes. When you get pg those chromosomes come together. The last chromosome to come together is the male one. Whatever that chromosome is determines the sex of the baby. Whether it is a Y or X, that is the what makes the sex of the baby. So, the male determines the sex, not the female.

I hope I explained it right.

Karen

DisneyGirl
06-04-2006, 09:56 AM
This is what we were told when we went for genetic counseling:

Both men and women have 23 chromosomes. When you get pg those chromosomes come together. The last chromosome to come together is the male one. Whatever that chromosome is determines the sex of the baby. Whether it is a Y or X, that is the what makes the sex of the baby. So, the male determines the sex, not the female.

I hope I explained it right.

Karen

That is how i understood it to work as well.

lawgirl4
06-04-2006, 11:53 AM
I don't think there's any denial that yes, the sperm - and hence the male - provides either the "X" or "Y" chromosome, which determines whether the baby is a girl (XX) or a boy (XY).

However, given the OP's SIL's statement, I think the question here was more focused on "secondary" factors that assist in gender determination - such as variations in cervical PH (which may favor X or Y sperm) or variations in the PH of the egg coating, both of which were noted above.

So yes, ultimately it's the sperm that determines gender, but clearly the female reproductive system plays a role in the likelihood of X vs Y sperm fertilization, and hence can influence gender determination/outcome.

cosmic
06-04-2006, 12:06 PM
The last chromosome to come together is the male one. Whatever that chromosome is determines the sex of the baby. Whether it is a Y or X, that is the what makes the sex of the baby. So, the male determines the sex, not the female.

I hope I explained it right.

Karen

Yes, that's the way it was explained to me too. :)

BTB
06-04-2006, 12:08 PM
Yes, of course the sperm provides the second chromosome, ultimately determining gender. But all is not as simple as Bio 101 would lead one to think - the egg is not a passive recipient, equally hospitable to all sperm. I agree with soulmate.