A Study of the Chromosomes in the Cat

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Abstract
Chromosomes were studied in 6 Felis domestica kittens (3 males and 3 females) 2 or 3 days in age having white, orange and tabby tortoiseshell coat colors, respectively. Diagnosis of chromosomes was based on cells from kidney and heart cultures. Testicular tissues of an adult black cat were also observed in squashed preparations. Twelve metaphasic cells from 5 kittens were found to possess the diploid chromosome number (38). Referring to the size, shape and the position of the centromere, 38 chromosomes were tentatively classified into 6 groups of autosomes and a pair of sex chromosomes. Karyotype analyses revealed that the chromosomes were essentially the same in all the kittens, except for an XY-mechanism in males, and XX-mechanism in females. The X-element with a submedian centromere was found to correspond to the 14th autosomal pair in size. The Y-chromosome having a subterminal centromere corresponded to the smallest metacentric autosome in size. In the kidney culture cells from a presumptive tabby tortoiseshell male cat were found 38 chromosomes of a normal male complement. The origin of male tortoiseshell cats was discussed from the standpoint of their chromosome number.