is it just random? i've learnt bout homozygote and heterozygote.stuffs like that.mendel's laws.but all those are just probabilities.how do they (just use they) actually decide the gender?
2006-08-01 04:33:37 · 7 answers · asked by danyelle 1 in Science & Mathematics ➔ Biology
Gender is determined by whether the fetus has two X chromosomes, or an X and a Y--it has nothing to do with the brain.
This is determined by which sperm reaches the egg first(each sperm has either an an X or a Y, whereas every egg has an X), so it's decided at the instant of conception.
2006-08-01 04:47:35 · answer #1 · answered by Sean 5 · 1⤊ 0⤋
The brain, per se, has nothing to do with it. I believe your question is - what determine's gender in humans (mammals). In this case, it's whether or not the zygote carries a Y chromosome plus and X Chromosome or whether it carries two X chromosomes. An XY is a male; an XX is female.
There's a WHOLE set of chemistry that comes in after that, but the fact that the egg has either a Y sperm or an X sperm to fertilize it is what determines gender (in mammals).
In other animals, it ain't the same.
2006-08-01 11:50:19 · answer #2 · answered by Anonymous · 0⤊ 0⤋
The basis of physical gender/sex is within the chromosomes - which, if all goes well, will cause the fetus' testes or ovaries to start producing the appropriate hormones which set the future person's gender identity in their brain. If something happens in utereo to interfere with the appropriate amount of the "correct" hormone reaching the brain then the individual may be transgendered.
2006-08-02 16:58:49 · answer #3 · answered by Drewe 3 · 0⤊ 0⤋
The brain doesn't decide. It's decided at the instant the sperm enters the egg. All eggs carry only the X chromosome, but sperm carry either the X or Y chromosome, so whichever one fertilizes the egg determines what the sex will be. So Mendel's law doesn't apply here--the DNA is located inside the egg and sperm, and the strands of DNA don't start to combine until the two join. It's Mendel's law which determines which DNA, that of the egg or that of the sperm, will be dominant.
2006-08-01 11:47:47 · answer #4 · answered by cross-stitch kelly 7 · 0⤊ 0⤋
Hormone concentrations feminize or masculinizes the brain.
Androgens, like testosterone masculinize the brain and an absence of testosterone and a presence of estrodiol feminizes the brain.
2006-08-01 15:38:41 · answer #5 · answered by Stephanie S 6 · 0⤊ 0⤋
it isn't the brain that decides, the chromosomes do. if the baby has two X chromosomes it will be female, if it has an X chromosome
& a Y chromosome it will be male =)
2006-08-01 11:55:20 · answer #6 · answered by Sparkle 2 · 0⤊ 0⤋
the brain doesn't decide gender, the sperm does
2006-08-01 13:17:26 · answer #7 · answered by ~Perfectly Flawed~ 3 · 0⤊ 0⤋