Epigenetics Why Women Are Stripey

Epigenetics means women have different active x-chromosomes in different cells.

When a female embryo is four days old it consists of just 100 cells. At this point the x-chromosome from Mom and the one from Dad are both active. But in order for proper development to occur, one of the x chromosomes must be switched off.

Through a tiny molecular battle within each cell, one of the x-chromosomes wins and remains active while the loser is deactivated.

This is done by wrapping the DNA tighter around proteins, modifying histone tails, and DNA methylation - molecular markers to indicate this DNA should not be read.

What's surprising is that it's pretty random which x chromosome wins - sometimes it's Mom's and sometimes it's Dad's. So when a female is just 100 cells big, her cells have a mix of active x-chromosomes, some from Mom and some from Dad.

~~DISCUSSION~~