Genetics (Extra Credit)

The nucleus in the cells in our bodies contain genes,
It doesn't matter if you an adult, kid, or teen.
In between 20 and 25 thousand genes make up one chromosome,
And alleles tell how you will look but not where you will roam.
X and Y tells if you are a girl or boy,
But it won't tell who you will annoy.
As generations go on, more people are closely related to you,
And parents can pass genes for allergies that can make you go achoo.
Genes can make a boy colorblind,
And they also control part of what is in your mind.