Medical Research Council - London Institute of Medical Sciences

Now in our 10th year of bringing you beautiful imagery from biomedical science every day

Calico Colours
24 September 2013

Calico Colours

This beautiful moggy is a calico cat, and animals with this kind of blotchy fur patterning are thought to bring good luck in many cultures around the world. But as well as looking pretty, the calico cat’s coat can tell us a lot about genetics. Virtually all calico cats are female, meaning they carry two X chromosomes while male cats have an X and a Y. To compensate for this double dosage, one X chromosome is randomly switched off in every cell as a female kitten grows in the womb. The orange and black fur colour genes are also carried on the X chromosomes, and if a female cat inherits one ‘orange’ and one ‘black’ X chromosome, the colours will be randomly switched off too, giving the characteristic calico pattern. The white blotches come from a gene on another chromosome, but that’s a different tale (or tail?) altogether.

Written by Kat Arney

  • Originally published under a GNU Free Documentation License

Search The Archive

Submit An Image

What is BPoD?

BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.

Read More

BPoD is also available in Catalan at with translations by the University of Valencia.