Women/Females are Stripey!

No, I am not being sexist here. This is a fact. This short video by Veritasium explains it.

How/Why??

This is the result of epigenetics. As we know, humans have 46 chromosomes including a pair of sex chromosomes. XX for females and XY for males. In the reproduction process, the female ovum (egg) and the male sperm contributes an equal amount of chromosomes (23 each). From the moment of fertilization until the embryo is ~100 cells in size, both X chromosomes from mom and dad are active.

In order for development to proceed, one of the X chromosomes have to be deactivated. This process occurs during the 100 cell size period where one of the X chromosomes randomly gets deactivated in the cell through a "molecular battle". The losing X chromosome gets packed into a smaller size and marker groups are added to signal the cell that that X chromosome should not be used.

Since females have two X chromosomes, they are technically stripey as the amount of X chromosomes from mom and dad during the 100 cell size is random and continues to develop into an adult. We cannot actually see them in humans but we can see them in kitties.

Calico cat. From Wikipedia.