In female placental mammals with an X-Y sex determination, X chromosome inactivation is used to achieve dosage compensation of the expression of X-linked genes in female and male individuals. Inactivated X chromosomes that appear as dark-staining spots within the cell nuclei are referred to as Barr bodies.
Individuals that have the genotype XXXY exhibit the phenotype of Klinefelter Syndrome and should have
Barr bodies in each of their cells, while individuals with the genotype XO exhibit the phenotype of Turner Syndrome and should have
Barr bodies in each of their cells.