Male and Female Calico Cats

Genetic contributions and the Klinefelter Syndrome in males

by Matt Rudie

  • Female Calico Cat Genotype
  • X-Inactivation Video
  • Male Cats Genotype
  • Male Calico Cats and Klinefelter Syndrome
  • History and Effects Klinefelter Syndrome

Female Calico Cat Genotype

  • Fur color caused by two alleles on X chromosome Xo=black and XO=orange
  • Female (XX) can be all black all orange or a mix of the two if heterozygous
  • Pattern of calico fur patches caused by inactivation of one of the X chromosomes randomly in a process known as lyonization
  • Some orange fur genes are inactivated and code for black and vice versa
  • White Fur results when color pigment is not expressed
X Inactivation

Male Cat Genotype

  • Male Genotype XY
  • Can be either Black (XoY) or Orange (XOY)
  • Possible to get a male calico?

Male Calico Cat and Klinefelter Syndrome

  • Only possible if genotype coded for more than one fur color
  • Calico male cats are resulting from a genetic anomoly known as Klinefelter Syndrome
  • Genotype is XXY allowing for one X to code for orange and one code for black, producing the calico fur pattern commonly seen only in females.
  • XXY genotype can occur during Meiosis 1 when homologous chromosomes seperate
  • Only problem is one of the chromosomes does not separate creating a XY germ cell

History and effects of Klinefelter Syndrome

  • Discovered in 1942 by Harry Klinefelter
  • Once believed to be caused by endocrine malfunction
  • Occurs when homologous chromosomes fail to separate during meiosis 1
  • Results in reduced levels of testosterone, incomplete puberty, breast enlargement, infertility, risk of breast cancer, and delayed speech and language development
  • Often causes social problems among children afflicted with the disease


Many children afflicted with Klinefelter Syndrome face problems aside from the disease itself. Many of those afflicted experience depression and often battle with acceptance by peers. This prevalent yet seemingly unknown syndrome still has not cure, but some treatments are available. Further research, public knowledge, and understanding of the mechanics of this disorder must be undertaken to ensure that those battling with this disease are not ostracized or shunned by their peers for something that is out of their control. Many genetic anomolies in children often result in this social acceptance, which generally diminishes their well being. Education of the nature of disease like Klinefelter syndrome could be beneficial to many K-12 students in promoting critically thinking about how our body functions and grows instead of allowing misunderstanding to lead to unjustified bullying.


Bojesen, A. and C. H. Gravholt . 2007. Klinefelter syndrome in clinical practice. Nature Reviews Urology 4:192-204

Bojesen, A. and C. H. Gravholt. 2011. Morbidity and Mortality in Klinefelter syndrome (47, XXY). Acta Pediatrica 100:807-813

Centerwall, W. R. and K. Benirschke. 1972. Male tortoiseshell and calico (C-T) cats. The Journal of Heredity 64:272-278

Lyle, S. K. 2007. Disorders of Sexual Development of the Dog and Cat. Theriogenology 68:338-343

Visootsak, J., and J. M. Graham. 2006. Klinefelter syndrome and other sex chromosomal aneuplodies. Orphanet Journal of Rare Diseases 1:1-42

Image and Video References