On Mochi, the Hamada Family’s Male Calico Cat

So I’ve heard some stuff going ‘round at how Mochi is supposed to be a female cat since it’s a calico cat, contrary to supplementary material, where Hiro uses male pronouns to address Mochi. For a long time after seeing the movie, I thought that “heh, the official material’s a bit wrong there lmao” but then after thinking about it for a while I realised that, yes, they’re actually right, or at least possibly right about Mochi being a male calico rather than a female calico. Lots of science under the cut.

I legit spent half an hour on this. Wow. Not sure if someone’s actually explained this before or that I’m a total nerdy loser lmao

There’s this thing called the Klinefelter Syndrome, it’s a genetic disorder involving the sex chromosomes of an individual. It affects Y chromosome-carrying individual physical and cognitive development, and the symptoms vary among individuals, many of them not even manifesting at all in affected individuals.

The Klinefelter Syndrome results from an addition of an extra X chromosome in the cells of the Y-carrying individual, so instead of the usual XY that males carry, Klinefelter individuals have a genotype of XXY.

(image source: http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Human_chromosomesXXY01.png/768px-Human_chromosomesXXY01.png)

This genetic condition actually occurs pretty frequently, in an estimated 1:500 to 1:1,000 human male live births. The addition of the extra X chromosome comes in the nondisjuction of the sex chromosomes during division of the sex cells of the individual’s parent, resulting in one sex cell possessing two sex chromosomes, and its partner, having none (if that got fertilised it would bring about another genetic disorder, the Turner Syndrome). The sex cell having the two sex chromosomes would then be fertilised and would bring about the individual having the XXY genotype.

Now, in cats, colour is genetically inherited through the sex chromosomes. Specifically, the X chromosomes. Each X chromosome carries a gene for a certain fur colour, there’s orange, black, et cetera. For a cat to be a calico cat, it must express both colour gene-linked X chromosomes, so it has to have, for example, an X(orange)X(black) genotype to express the calico pattern. The differing patches of colour happens due to the action of X-chromosome inactivation, or Barr body formation, which is a mechanism of the body to avoid double- or over-expression of any genes on the nearly-identical X-chromosomes. One X-chromosome is inactive per area of colour, so the other still active one will express its colour, giving the cat’s coat the calico patterning we’re all familiar with.

(image source: http://img1.wikia.nocookie.net/__cb20140925154631/disney/images/4/48/Big-Hero-6-49.png)

That being said, calico cats should generally be female, but male cats can be calico cats, if they have genetic abnormalities, like having two X-chromosomes, meaning, they have to be sterile Klinefelter individuals. They’re actually kinda common, with approximately 1 male in 3,000 calico individuals.

So, Mochi can be male. Whod’ve thought.

tl;dr: Mochi may have a genetic disorder that lets him be a calico cat even though he’s male. That’s it lmao gomen for the science

References:

Bock, Robert (August 1993). “Understanding Klinefelter Syndrome: A Guide for XXY Males and their Families”. NIH Pub. No. 93-3202. Eunice Kennedy Shriver National Institute of Child Health and Human Development. Retrieved December 13 2014.

Centerwall WR, Benirschke K (1975). “An animal model for the XXY Klinefelter’s syndrome in man: Tortoiseshell and calico male cats”. American journal of veterinary research 36 (9): 1275–1280.

“Klinefelter Syndrome”. Health Information. Eunice Kennedy Shriver National Institute of Child Health and Human Development. 2007-02-19. Retrieved December 13 2014.

Spadafori, Gina. “Feline Fallacies”. The Pet Connection. VeterinaryPartner.com. Retrieved December 13 2014.