Chromosomal analysis of all of the following genotype shows Barr bodies, EXCEPT:
Routine microscopy of mammalian cell nuclei reveals a small, dense mass of heterochromatin present in females but not males. This "sex chromatin" (or Barr body or X-chromatin) is one of the two X chromosomes present in females. As a general rule, only 1 X chromosome functions in a cell at a given time. All other X chromosomes present in a cell may be seen as X-chromatin bodies in a resting nucleus. Thus, if one knows the number of X chromosomes, one can anticipate that the number of Barr bodies will be 1 less. If one counts the number of Barr bodies, the number of X chromosomes can be determined by adding 1. Hence Barr bodies are not seen in genotype XO. The male cell has one X chromosome and one Y chromosome, therefore no sex chromatin is visible in males. Ref: Manipalviratn S., Trivax B., Huang A. (2013). Chapter 3. Genetic Disorders & Sex Chromosome Abnormalities. In A.H. DeCherney, L. Nathan, N. Laufer, A.S. Roman (Eds), CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 11e.
XO
XXY
XX
XXX