Genetics as it applies to evolution, molecular biology, and medical aspects.
Usually, the possibility to produce a boy or a girl is the same.. 50%
But, I read my book.. It said that a boy is often produced than a girl... That is happened because the Y chromosome can live longer than X chromosome
Do you think it is true?
chromosomes aren't alive.
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
Actually it is postulated that sperm containing an x chromosone (female) can live longer than sperm containing a y chromosone. Supposedly although the female sperm may live longer, the mobility is reduced, while male sperm swim faster. This means that the likelyhood of having a male or female child is also affected by when you attempt to concieve in relation to when you ovulate.
This implies that, for example- if you were to copulate a day or so before you are due to ovulate then by the time ovulation takes place most of the male sperm would be effectively dead, while if the female sperm do infact live longer- they are still swimming.
I've heard the y-chromosome = fast, x-chromosome = resilient thing before also. Let me know if this is too off-topic but my teacher said the other day that the birth rate of boys during war time is higher than that of girls and when I asked her why she said something about the acidity of the vagina but didn't say anything more.
I have since tried to work out why/how this would happen and I would like to hear what other people think about it:
I thought that during a war women would probably be under more stress than usual. I then thought that stress may cause the body to generally raise the defences (including the acidity in the vagina). This is where the x-chromosome, y-chromosome thing comes in (so it is kinda related) because I wasn't sure how the "male" sperm would be able to survive the higher acidity better than "female" sperm. It would seem that the speed would allow it a better chance, but I'm a bit unsure as to how that would work.
I would appreciate people's opinions, and just let me know (nicely) if this was too off-topic.
That's an intersting thought. Hmm. I suppose the claims of a higher birthrate of boys during wartime could be supported using statistical data, I also suppose that records of womens acids level could be obtained through historical medical data.
Maybe the womans biological instinct to preserve the species (Make more soldiers) triggers a hormone to produce more acid, thus a speedy delivery would enhance the odds of a male sperm, since slower moving sperm would be destroyed by the acid.
Cool post, or should I say Gday
Heh, thanks. I'm not sure of the typical Californian greeting, but I appreciate your cultural knowledge
As for the birth rate, I had the same idea about preservation of the species = higher acidity levels but a friend pointed out that the body probably wouldn't know that the species was under threat and needed more boys, which is why I thought of the stress triggering hormones theory. This seemed to make more sense to me, because I figure that it could have come about quite easily through natural selection, i.e. tribes (back in the day) where the females happened to react to stress in a way that raised the acidity would produce more boys (I do think that your theory of slow moving sperm being more susceptible might work) and be victorious, passing on their genes etc. etc.
Let me know whether you think my theories are plausible and add in/subtract bits as you feel the need. Feel free original poster to steer me back onto the subject if this is too far off (though it is about gender birth rates, I swear)
So... all the possibility are depends on environment and the acidity of the vagina , right ?
And the body will automatically react to the environment and producing the hormones
So in the end, I think the natural selection will work in producing more men than women...
I think that's the conclusion, Am I right ?
That's roughly what I'm thinking, stress = hormones = higher acidity . So the birth rate would depend on the environment, though I don't think natural selection would produce more boys overall as, for reproductive purposes, usually more girls than boys would be advantageous; more boys would only really be useful in times of stress (I think).
Cool article! It reminded me of a question I asked my teacher when we were learning about Polysomy that she couldn't answer, but I might give it a try here. My teacher told us that Polysomic (if it wasn't a word before, it is now) sperm had a lesser chance of fertilising an egg because of the weight of the extra chromosome. I asked whether that would mean that in artificial insemination of various kinds there was a higher chance of Polysomy. She couldn't say, but I thought maybe someone here has heard of it.
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