Sex chromosome wiki

Outside North America, the pattern is more usually called tortoiseshell and white. Calico” refers only to a color pattern on the fur, not to sex chromosome wiki breed or two-colored eyes on a cat. Because genetic determination of coat colors in calico cats is linked to the X chromosome, calicoes are nearly always female, with one color linked to the maternal X chromosome and a second color linked to the paternal X chromosome.

There is also a type of calico cat referred to as a dilute calico. Dilute calicos are not necessarily rare. They are recognized by their grey, silver, and gold colors instead of the traditional white, black, brown or red patched coat of a calico. Dilute calicos are also called light calicos, because they usually have no dark-colored fur. However, the existence of patches in calico cats was traced to a certain degree by Neil Todd in a study determining the migration of domesticated cats along trade routes in Europe and Northern Africa.

Two calico cats from the same litter with different markings. In genetic terms, calico cats are tortoiseshells in every way, except that in addition they express a white spotting gene. There is however one anomaly: as a rule of thumb the larger the areas of white, the fewer and larger the patches of ginger and dark or tabby coat. Serious study of calico cats seems to have begun about 1948 when Murray Barr and his graduate student E. Bertram noticed dark, drumstick-shaped masses inside the nuclei of nerve cells of female cats, but not in male cats. These dark masses became known as Barr bodies. One exception is that in rare cases faulty cell division may leave an extra X chromosome in one of the gametes that produced the male cat.

That extra X then is reproduced in each of his cells, a condition referred to as XXY, or Klinefelter syndrome. All but about one in three thousand of the rare calico or tortoiseshell male cats are sterile because of the chromosome abnormality, and breeders reject any exceptions for stud purposes because they generally are of poor physical quality and fertility. The mutation that gives male cats a ginger-colored coat and females ginger, tortoiseshell, or calico coats produced a particularly telling map. The orange mutant gene is found only on the X, or female, chromosome.

As with humans, female cats have paired sex chromosomes, XX, and male cats have XY sex chromosomes. The female cat, therefore, can have the orange mutant gene on one X chromosome and the gene for a black coat on the other. The piebald gene is on a different chromosome. It is currently impossible to reproduce the fur patterns of calico cats by cloning. Penelope Tsernoglou wrote “This is due to an effect called x-linked inactivation which involves the random inactivation of one of the X chromosomes.

Since all female mammals have two X chromosomes, one might wonder if this phenomenon could have a more widespread impact on cloning in the future. Calico cats may have already provided findings relating to physiological differences between male and female mammals. Cats of this coloration are believed to bring good luck in the folklore of many cultures. In the United States, these are sometimes referred to as money cats. New York: Macmillan Reference USA, 2003. Shrinking the Cat:Genetic Engineering before We Knew about Genes.

Genetics for Cat Breeders and Veterinarians, Butterworth-Heinemann Medical, 1991. Transcriptional Regulation of an Entire Chromosome: Dosage Compensation. To Clone or Not to Clone: A Look at Why Cloning Fluffy and Fido Might Not Be in the Best Interests of Society and May Inevitably Pave the Way for Human Cloning. Feline Folktails – Cats in Folklore and Superstition”. Language in the USA: Themes for the Twenty-first Century”.