Who determines the sex of the baby?

Question

Has anyone heard of a scientific reason that women can determine the sex?

Answer 1

The generally accepted theory is that males determine the sex because males can donate both an X chromosome or Y chromosome, while females can only donate an X chromosome to their offspring, making their contribution constant and the male's contribution the variable which, under normal circumstances, determines the offspring's genetic sex... at least, in humans*.

That said, though, that doesn't mean every human being out there has had their sex determined by their father and not their mother.

Under certain circumstances, if the female parent is producing abnormally high quantities of testosterone during the very early stages of pregnancy, even though the fetus is of XX genetic make-up, the mother's hormones can influence it to develop into a perfectly normal male, even without a Y chromosome (since, once male anatomy develops it will naturally take over producing the androgens the male will need for the rest of his life).

On the other hand, if an XY fetus cannot produce enough androgens to cancel out the estrogen and progesterone being produced by its mother (either because the fetus simply isn't producing adequate androgens or because the female is producing unusually high levels of feminizing hormones), it can develop into a perfectly normal female, despite having both an X and Y chromosome (again, the developed female anatomy will normally function to produce all the female hormones she needs in life).

There is some suggestion that females produced in this fashion (with an X and Y chromosome) could have an athletic advantage over females who have two X chromosomes... which is why, these days, all athletes which compete in the Olympics and in various other competitions of that type are administered a "Barr Body" test.

Contrary to popular opinion, females don't really have two X chromosomes any more than males do. They start out with two, but as they develop, their body chooses the stronger of the two X chromosomes as the active one, and the weaker X "atrophies" into a small compact ball of genetic material known as a Barr Body. If a female has a Barr Body, then you know she has two X chromosomes without having to actually go to the trouble of doing in depth genetic testing.

If she doesn't have a Barr Body, you know she had no second X chromosome to dispense with, and therefore is an XY female.

So, the answer is if everything goes right, the father determines the sex of the child by donating the chromosome which determines what sex it is supposed to be, but our biology is adaptable enough that if something goes wrong hormonally during pregnancy, we can still develop "normally" and have no problems in life, with our mother having actually determined what our sex ended up being.

More to the point, if somehow you found two individuals, a male who had two X chromosomes, and an XY female, it would actually be the mother which donated the chromosome to genetically determine the offspring's sex, though the odds of that happening are extraordinarily low. Still, one in a billion odds means it's probably happened half a dozen times in the people alive today. It's just not the normal course of events for our species.

And, of course, there are a whole slew of things that can go wrong to cause the fetus to develop abnormally, but that's another matter.



*Different species actually determine offspring sex in different ways. For instance, in mammals those members with XY chromosomes are males and XX chromosomes are females. However, in birds females have XY chromosomes and males have XX chromosomes... and in alligators, crocodiles, etc, the sex of the offspring is actually determined by the temperature at which the eggs incubate. There are even species of fish (most notably the Sunfish), in which all members of the species start out as males and then spontaneously change sex to females after the first ten years of their lives or so. In wrasses (a type of reef fish), if all the males are taken out of a population-- say if they're killed-- the largest of the females will immediately begin to behave like a male and within ten days will change sex and begin producing sperm. So, Nature has all sorts of ways to make the "male or female" decision. If you'd like an interesting article on the subject, go here:

http://www.stanford.edu/dept/news/pr/03/aaassocialselection219.html

Addendum: I didn't get into this because it's really not a part of normal "sex selection", but as another poster has brought up the subject, XXY children, or XXXY children, or even XXXXY children (the genetic disorder is known as Klinefelter's Syndrome), will end up male, not female. The presence of a Y chromosome will override all X chromosomes present to produce a male child (though granted one suffering from certain disorders because of the faulty genetic structure... Klinefelter's males are almost always sterile, usually have problems with speech, often suffer from gynecomastia, have an increased risk of breast cancer from normal males, etc), no matter how many X chromosomes are present.

Answer 2

Well, one possibility exists, but it is very slim. Say you have a woman (stretching it), who has a XXY genotype. If she were to be able to reproduce as a woman, (most likely she would be infertile, but just for the heck of it), during meiosis she could create an egg with a X, XX, XY, or Y genotype. Again this is stretching it. But if the male donated a sperm with a X genotype, and the female gave an egg with the Y chromosome, and it was carried to term, then yes, the female would have determined the sex of the baby. Pretty weird if it did happen though.


P.S. While I am one who believes in God, he might influence things once in a while, but I don't think he's always determining the sex of a baby. He set the system that works, just like evolution. There's a lot of crazy ignorant christians out there, so anyway, that's my two bits.

Answer 3

The father is the carrier of the sex chromosome. If an X chromosome is present in the genotype, the baby will be female, and in case of an Y chromosome thebaby will be male.

Women have no role in determination of baby's sex.

However, there are some unproved theories about sex determination by woman. One of these is the position of a woman during sex - if a woman lays on her right-hand side, the baby will be male, and if she is in a doggy position (from behind), the baby will be female.

But that is all rubbish, because genetics recognises no other way of sex determination but the shape of sexual chromosome.

And stop asking questions with well-known answers.

Answer 4

Gender selection of children is a controversial topic, particularly in terms of genetic therapy and the ethics of picking the sex of your child. While there certainly have been advances in the field of genetics, there are actually some natural and completely ethical things that you can do that will increase the likelihood of selecting a gender for your child.

Check this video for more info - http://tinyurl.com/PlanMyBabyGen

While no method is 100% accurate, if you are determined to have a boy or a girl, there are a few things that can be done to significantly increase your chances of conceiving the gender of your choice. Remember, the most important thing is to have a healthy baby, regardless of their gender. But if you do want to try to pick the gender of your child, it is possible. Here's what you need to know.
Differences in Sperm
The sperm that carry the Y chromosome are the "boy" sperms, while the ones that carry the X chromosome are the "girl" sperms. The Y sperm are faster, smaller, more agile but they do not last as long as the "girl" sperm. The X sperm are bigger and move quite slowly. In addition to their overall speed, they have different preferences in terms of the acidity of the vagina and cervix. An X sperm does better in an acidic environment while the Y sperm prefer an alkaline environment.
How These Differences Affect Conception
Now that we have established the differences between the sperm that carry different chromosomes, it is important to understand how these differences can be used for natural gender selection. Once you have this information, you can begin trying to conceive a child that will be a specific gender.
If you want to have a boy, the timing is crucial. Since these sperm do not live long, it is vital to time your intercourse as closely to ovulation as possible. This gives the Y sperm time to reach the egg before the X sperm do, increasing the chances that you will have a boy.
If you want to have a girl, you need to give the X sperm plenty of time to reach the egg. Since they live longer, this means that you want to time intercourse a few days before expected ovulation. By the time you ovulate, the Y sperm will have already died off, leaving only the X sperm behind. They will have the time needed to travel up through the cervix to reach the egg and fertilize it.

With over a 94% success rate, what do you have to lose? Check this video - http://tinyurl.com/PlanMyBabyGen

Answer 5

This Site Might Help You.

RE:
Who determines the sex of the baby?
Has anyone heard of a scientific reason that women can determine the sex?

Answer 6

It's the male who determines the sex (not that he chooses deliberately; it's really chance). The female always contributes an X chromosome, and the male either contributes an X or a Y. Two X's makes a female, and XY makes a male.

Answer 7

Mother nature?

Seriously, I think it's the male that determines the sex
of the baby. If your question was if a woman can choose
the sex of the baby, I'm sure with a help from a
fertilitry specialist it's possible.

Answer 8

While the man's sperm have either X or Y chromosomes, I have read that the atmosphere around the woman's egg can influence which ones would have a better chance to succeed.

So, I guess the man's sperm determines the sex, but the woman can rig the race?

Answer 9

it is the male who determines the sex of a baby

Answer 10

XY= Male
XX =Female

Although there are things like genetic alterations under the heading "Family Balancing" as some has pointed out, there is no natural or nutritional way the female can intentionally influence the sex of her child.

Although there are pagan or historically influenced myths & rituals, there has been no successful genetic way it can be done with out the help of science & Technology, Although I would not attempt it, try to be happy with what you get and try to keep the child healthy.