BARRBOD - HUMAN SEX CHROMOSOMES AND BARR BODIES THE XY...

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HUMAN SEX CHROMOSOMES AND BARR BODIES THE XY SYSTEM In   humans   and   most   other   mammals,   the   presence   of   the   Y   chromosome  appears to determine a tendency for maleness; males are chromosomally XY and  females are XX. Since the male produces two types of gametes at meiosis with regard to the sex  chromosomes, he is referred to as the heterogametic sex.   Since the female can  produce only one type  of  gamete  in  regard  to  the  sex  chromosomes,  this is  the  homogametic sex. This results in a 1:1 sex ratio among the progeny in the next  generation. The   gene   believed   to   be   the   genetic   switch   for   determining   maleness,   the  testicular determining factor (TDF), has recently been assigned to region IA2 on the  short arm of the Y chromosome.  Precisely what this does is unknown, but its presence  causes the undifferentiated gonad to become a functional testis.  Further development  of   maleness,   such   as   secondary   sexual   characteristics,   comes   about   through   the  influence of testosterone produced by the functional testis. DOSAGE COMPENSATION AND FALCULTATIVE HETEROCHROMATIN
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This note was uploaded on 05/03/2008 for the course BIO 2322 taught by Professor Spotswood during the Spring '08 term at The University of Texas at San Antonio- San Antonio.

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BARRBOD - HUMAN SEX CHROMOSOMES AND BARR BODIES THE XY...

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