It's Tuesday! The day of brain droppings....
*I need to redo this picture... The brain is supposed to be hopping
AWAY from the jar but we all read left to right so.....
Basic genetics 101:
Mammals have X and Y sex chromosomes...
If you're a guy, you have X (from mom) and Y (from dad).
If you're a girl, you have X (from mom) and X (from dad).
Sex chromosomes have thousands of genes with much wider effects than just sex differences. For example, the X chromosome determines coat color in kitties.
Normally, in the womb, the little developing female kitty decides which of the two Xs to keep (mom's or dads).... cuz you only need one... and it suppresses the other. Sometimes, this suppression fails and the genes from both Xs are expressed.
Enter calico cats!
Their coat is a physical representation of this effect (1/2 coat color from mom, 1/2 from dad).
Because this only occurs with two X chromosomes, calico cats are almost* always female!
*The exception is the rare XXY male.
Your turn! Got a cool fact to share with me?