This weeks Science Saturday is all about DNA, specifically the inner workings specific to womens DNA (who have two X chromosomes).
Men have both an X and a Y chromosome, but women have two X chromosomes. But this inevitably means that one of the two X chromosomes needs to be “silenced” or turned off. This is done by way of a molecular battle within a cell and one X chromosome is turned off whilst the other remains fully functional.
What’s interesting is the fact that the X chromosome that wins is completely random. In some cells Dad’s X chromosome wins, in other cells Mum’s X chromosome wins. This means that the 100 cell embryo (the point in a child’s development that the X chromosomes are turned off or kept on) means it has a mixture of both Mums and Dads active X chromosomes, and as the cells divide, they maintain the particular active X chromosome they started off with. And this continues on into adulthood.
So if you could look at a womans skin and see which particular X chromosome has been inactivated, you’d see a kind of stripey pattern, which essentially shows the growth and migration of all the first 100 cells when the embryo was only four days old.