An autosome is any chromosome that is not a sex chromosome (an allosome). The gene for carnosinase is located on chromosome 18, an autosome. The male (Y) chromosome has been translocated to the short arm of an autosome. The "Megupsilon" example was the first instance of autosome/Y chromosome fusion discovered in a fish. Ainsworth describes sex determination in the genus as using "an X/autosome dosage type". An autosome may be a more likely candidate for regulating this process in humans.