Biology / Unit 5 Bio 1075 short lesson, about 20 seconds
Sex-Determination Systems
Captions available
The idea
Sex-determination systems assign sex chromosomally: humans and most mammals use XY, some insects use XO, and birds and butterflies use ZW.
In practice
Human XY males are the heterogametic sex, while ZW birds reverse this — females, not males, carry the two different sex chromosomes.
Where people slip
Which chromosome type an organism inherits at fertilization is what Bio 1047's X-linked crosses assume, not derive.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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