Hypothesis: XX Males and XY Females Result 
from X-Y Interchange at Paternal Meiosis 
' ^ TDF 
X 
1/ 
I I 
g +TDF -TDF 
I 
XX male XY female 
The X-Y interchange hypothesis: XX males and XY females receive reciprocal 
products of similar aberrant XY exchanges occurring in the fathers during 
the production of sperm ( meiosis). TDF is testis-determining factor, the sex- 
determining gene normally located on the Y chromosome. 
Research of David Page. 
312 
