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Name: Darrow
Status: Other
Grade:  Other
Location: N/A
Country: United States
Date: September 2006


Question:
If males carry the x and y chromosomes and the female only carries the X, doesn't it make it more clear that males where first? In order ror the first to duplicate or make another it would need the same or of the same to duplicate. If there was only X chromosomes then there would be no males; with male being first you have the ability to produce female or male.



Replies:
Not all organisms use the X Y system. For example in birds the female is the one who is heterogametic (different sex chromosomes). In "lower" mammals the sex chromosomes are more equal in size. It appears that over evolutionary time, one of the sex chromosomes started losing genetic material to the other chromosome during unequal crossover. The main gene on the Y that determines maleness is the SRY and as long as it remains on the Y, this chromosome will be the one that determines maleness, at least in primates.

vanhoeck


Your theory does not explain sex determination in birds. Males are XX (or ZZ) and females are XY (or ZW).

Ron Baker, Ph.D.



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