The superior sex chromosome. The X chromosome is found in both males and females. Though the Y chromosome is the one that determines male or female (XX= female, XY=male), the X chromosome is the one that determines life. Without an X chromosome the Y chromosome will do no good. A body can survive on one X alone, it is called Turner Syndrome. A body can also survive with more than one X, a male with more than one X had Klinefelter's Syndrome, and a female has Triple X Syndrome.
So uh, yeah. Everybody out there should thank their parents for their chromosomes. And be grateful you have an X, the chromosome that gives life.