Barr bodies
A barr body[1] is an inactive X chromosome in female cells or the inactive Z in a male. Lyonization is the process where the chromosome is inactivated in species. In addition to this, it is thought to be down to complete chance as to which X chromosome is inactivated and it is still unknown to this day as to how the cell decide which X chromosome is to be made into a Barr body.
In men and women with more than one X chromosome, the number of Barr bodies visible at interphase is always one less than the total number of X chromosomes.
For example, a man with Klinefelters syndrome, with 47 chromosomes, XXY karyotype have two Barr bodies, whereas an female with Turners syndrome, with 45 chromosomes, XO karyotype does not have any Barr bodies[2].
References
- ↑ Barr body http://en.wikipedia.org/wiki/Barr_body September 3, 2014.
- ↑ Sloane.E, The Biology of Women, 4th Edition, Cengage Learning, 2002, pages 133