Did you know that, approximately, only one in every three thousand tricolor cats is male ? In cats, hair color is a characteristic that is linked to the sex chromosomes. As the professor of Biochemistry and Molecular Biology at the University of Murcia José Manuel López Nicolás explains in his book A scientist in the supermarket (Planeta, 2019) , cats have two sex chromosomes: the X is provided by the mother and the father. it can provide either the X or the Y chromosome. In this way, and like humans, a cat with XX chromosomes is female and a cat with XY sex chromosomes is male.
“In cats, the gene for the color orange is located on the X chromosome and may have an allele (each of the alternative forms that the same gene can have and which are manifested in specific modifications of its function) for the color black . Therefore, the only way for both alleles to occur together and combined with white is for there to be two X chromosomes, that is, for it to be a cat ”, explains the scientist in his book. “In general, males only have one other color besides white. For this reason, only one in every three thousand tricolor cats is male ”. So, when you see a cat with three different colors, you can almost certainly bet that it is a female.
A biochemical curiosity about the color of Siamese cats
López Nicolás also explains the role of an enzyme called tyrosinase in the color of Siamese cats. This protein helps to produce melanin, a pigment responsible for dark spots on the skin. In addition, Siamese cats have a mutation in their DNA that causes tyrosinase to be much more sensitive to temperature than it is in other cats.
Thus, when a Siamese cat has a normal body temperature, above 37 ° C, tyrosinase is inactive, and therefore the predominant color of this breed is light. “However, when the temperature drops, tyrosinase is activated and a series of enzymatic and chemical reactions are triggered that give rise to melanin, darkening their skin,” explains the expert. ” For this reason, when it is hot, the Siamese cat has a more white surface and, when it cools, it has more areas of dark color .” In the same way, the legs, ears and nose of the Siamese have more contact surface and lose heat more quickly than the torso or the back. “Of course, this denaturation is reversible, so that if the temperature drops below 34 ° C, tyrosinase is activated and melanin is produced. At that time, the fur turns black. “
