In a mosaic cat, all the cells come from one original embryo, but a mutation or abnormality occurs in a cell of the developing embryo resulting in a block or blocks of cells genetically different from the rest of the embryo. The addition of the extra chromosome usually results in infertility in the male.
Sperm cell: X fertilises an X egg = XX (normal female kitten). Sperm cell: Y fertilises an X egg = XY (normal male kitten). Sperm cell: XY fertilises an X egg = XXY (Klinefelter kitten). Sperm cell: Y fertilises an XX egg = XXY (Klinefelter kitten). Instead of the sex cell being X or Y, it is XY (from the father) or XX (from the mother), if the defective sex cell contributes to a cat pregnancy, the resulting male offspring will be XXY instead of XY, having received an additional X chromosome. In some cases, the paired chromosomes fail to separate (disjoin) as they should and instead of each daughter cell receiving 19 chromosomes, it receives 38. Why 19 and not 38? Gametes only contain 19 chromosomes so that when during fertilisation, the two cells combine to make the correct 38 chromosomes. The cells destined to be sperm or an egg undergo meiosis, in which the 38 chromosomes in the cell separate, and produce two new cells with 19 chromosomes each. The disorder occurs due to a random error (nondisjunction) in cell division that happens during meiosis which is the division of parent cells to produce gametes (sex cells). Male calico and tortie cats Klinefelter syndromeĪlso known as XXY syndrome, Klinefelter syndrome occurs when the male is born with an extra X chromosome, so instead of being XY, he is XXY. A search of the University of Minnesota website returned no information on calico males at all, however, one research paper discusses a survey of 4,598 male cats in the UK, 20 of whom were tortoiseshell, which makes a ratio of 1 in 229 or 0.43%. This is the same statistic quoted in Robinson’s Genetics for Cat Breeders and Veterinarians. It has been widely reported that the University of Minnesota found the incidence of male torties or calicos is 1 in 3,000. What is the chance of a male calico or tortie cat? His coat is black and ginger, and he also carries the white spotting gene (note the white on his paws and chest). The male will either be ginger or non-ginger, he cannot be a mixture of both like the female. If she inherits the O gene from both parents, she will be ginger. So, if she inherits the O gene from one parent and o (non-orange) from the other parent, she will be a random mix of orange and another colour (usually black). 
As both X chromosomes within the cell cannot be expressed, one is inactivated in a process called lyonsation. The female (XX) inherits one X chromosome from her mother and one from her father.
If the X chromosome carries the O gene, he will be orange, if it does not, he will be non-orange. The male (XY) only has one X chromosome, from his mother, and a Y chromosome from the father. The dominant gene responsible for orange is located on the X chromosome (which makes it sex-linked).
#Calico kitten code
Genes are located on the chromosomes and are tiny segments of DNA that act as a code that specifies the production of a protein, which do most of the work within the cells and are essential for the function and regulation of the body’s organs and tissues. Each chromosome is made up of matching pairs, which provides information from the mother and the father. The chromosomes are located within the nucleus of every cell. To recap, cats have 19 chromosome pairs, 18 autosomes and the sex chromosome pair of XX or XY. Reviewed by Dr Sam Kovac – Southern Cross Veterinary Clinic How are some male cats calico or tortie?Ĭalico and tortie cats are almost always female, which we have covered in our article on calico cats.
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