|The X chromosome. |
Public domain image.
The X chromosome has around 155 million DNA base pairs, or 1000-2000 genes. 1,098 of those genes code for proteins and consist of around 5% of all the DNA in human cells. The X chromosome is larger and carries more genes than the Y chromosome, which means that if a gene on the X chromosome codes for a disease, that recessive trait will apear in any male children, since there is no dominate gene to counteract it. This characteristic of the X chromosome is visible in the fact only female cats can be calico, for its the females carry the allele for color and it can only code for one color at a time.
Females get two X chromosomes and males an X and a Y; since the normal chromosome count is 46 in total, females are denoted as 46,XX and males 46XY. In all cells other than egg cells, one of the two X chromosomes is inactivated (called Lyonization) except for a small area called the pseudoautosomal region. Many of the genes in the pseudoautosomal region are necessary for human development.
|A graphic of triple X syndrome, with a male on the left and female on the right, by |
Silver Spoon, CC-BY-SA-3.0. SOURCE.
A video about genetics, which explains the role of chromosomes and DNA:
And if you want information about the other chromosome, stop by tomorrow--I also explain why there was speculation humanity would go extinct because of the Y chromosome. Just in case that interests you . . .
-----The Golden Eagle