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View Full Version : The X chromosome you inherit from your mother, is it either of her two X chromosomes?



Zewu
06-28-2003, 08:22 AM
As you probably know, a man inheritated an X chromosome from his mother, while he inheritated a Y chromosome from his father, and a woman inheritated one X chromosome from her mother, and another one from her father.

Now, I am wondering about this, the X chromosome that either sex inheritated from his/her mother, could that be either of her X chromosomes, or is it perhaps a combination of the two?

example:



XX XY XX XY
| | | |
\ / \ /
X Y - offspring, man | OR | X Y - offspring, man

Is it like the above example, where it would be a 50% chance of inheritating either of the mother's chromosomes.

other example:



___
|XX| XY
----- |
| |
\ /
X Y


Or is it like the other example, where the mother's X chromosome is a combination of her two X chromosomes.


Hope you can answer my question.


EDIT: never mind about the examples, I think you can understand my question in pure theory anyway

SourceCode
06-28-2003, 08:37 AM
When a female produces eggs, each one of them has one X chromosone. Every single one of them. When a male produces sperm, each one has either an X or a Y. If a sperm with an X fertilizes the egg you get a girl. When a sperm with a Y chromosone fertilizes the egg you get a guy. So no it does not matter which X, because every X in the female is in a different egg. The whole XX and XY thing is used to figure out the chance of how many will be girls/boys and how many will have sex linked diseases like being color blind etc. I think you were trying to make it more complicated than it really is:)

Shogun
06-28-2003, 11:09 AM
actouly the gender is not determined by the X & Y cromosons. It's determend by a protoin witch they make,sometimes they make the wrong protoin so it is posible for a female to be XY and a male to be XX. But it is very unusal.

Zach L.
06-28-2003, 11:30 AM
Then there are bizarre conditions like XXX, XXY, and XYY.

Oh no... biology is coming back to me. :rolleyes:

DDPhoenix
06-28-2003, 11:32 AM
I think both Shogun and SourceCode are right on this one: there's a protein called the "Testis-Determining Factor" made by a gene on the Y-chromosome that starts a whole sequence of events that lead to the development of a male fetus (activates and deactivates other genes/proteins). Without this gene and protein, the fetus will become female by default.

Out of curiosity, why do you ask?