What is the difference between xx and xy chromosomes?

Answer 1

First of all, you're mistaken if you asked yourself this question: XX is the female sex chromosome combination, and XY is male.

It's important to realise that this is the case in humans, but not in all animals. Other animals, for example insects, have different mechanisms for sex determination.

In humans, a fertilised egg cell will divide a few times. Then each cell will turn off all but one of its X chromosomes (the phrasing is because in rare cases a fertilized egg can end up with three or more X chromosomes). This is possible and necessary because one X is sufficient to produce the proteins encoded on it, hence two active X would result in twice the amounts needed.

If you now wondered whether an embryo can also survive and grow to adulthood with only one X and no other sex chromosomes, you are correct. This is called monosomy X and causes a condition known as Turner syndrome.

Any human with only X chromosomes will be female. The Y chromosome, which is much smaller than the X chromosome, carries some additional genes whose influence will set off several mechanisms which ultimately lead to the development as a male instead. A Y chromosome alone cannot sustain life as it does not contain many of the vital genes which are located on the X chromosome.

Answer 2

this was put by contributors on this website.

always xx represents for female because the x chromosome have such genes which are important foe femaleness while XY always represents male because the y chromosome is responsible for one's maleness because it have such kind of genes which gives maleness to anyone.

EDIT:

your question was why males were XX and females XY. not always are they like that, actually. they aren't supposed to be like that, however during meiosis, if the X chromosome and the Y chromosome in the sperm cells cross over and they cross over more than they are supposed to, the SRY gene that gives males all their sexual organs and makes them different than females, would then be on an X chromosome. if that X chromosome then went into an egg cell (also X) then you would have an XX organism, but because it has the SRY gene on one of the X chromosomes, it would activate making the organism a male rather than female. same thing could happen but the other way, the Y sperm cell could go into the egg, but without the SRY gene, the organism would develop as a female.

Read more: Why_is_xx_a_male_and_xy_a_female

Answer 3

Females have two X chromosomes, and males have one X and one Y. Why are they called "X" or "Y"? A somewhat practical reason, actually- that is their shape.

Answer 4

xx is girl
xy is boy

Answer 5

male