X chromosome. Computer illustration of a human X chromosome, one of the two sex chromosomes. The red dots mark the areas of telomeres, the ends of the chromosome. The banding patterns created by staining the chromosome are represented by blue dots. Each type of chromosome can be identified by its unique banding pattern. Within almost every human cell are 46 chromosomes of which 22 pairs are the same in females and males. The last pair is composed of two X chromosomes for a female whereas a male has one X and one Y chromosome. In cells of a normal female, one of the X chromosomes is inactivated early in embryonic life and remains inactive ever after.