XY The nuclei of human cells contain 22 autosomes and 2 sex chromosomes. In females, the sex chromosomes are the 2 X chromosomes. Males have one X chromosome and one Y chromosome. The presence of the Y chromosome is decisive for unleashing the developmental program that leads to a baby boy.
So these little pieces tell us if we’re girls or hunks, actually this should’ve been a post about a new Valentine’s card, sorry about that..