The cat (Felis catus), also known as the domestic cat or housecat to distinguish it from other felines and felids, is a small furrydomesticated carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests. Cats have been associated with humans for at least 9,500 years, and are currently the most popular pet in the world. Owing to their close association with humans, cats are now found almost everywhere in the world.
Cats are similar in anatomy to the other felids, with strong, flexible bodies, quick reflexes, sharp retractable claws, and teeth adapted to killing small prey. As nocturnal predators, cats use their acute hearing and ability to see in near darkness to locate prey. Not only can cats hear sounds too faint for human ears, they can also hear sounds higher in frequency than humans can perceive. This is because the usual prey of cats (particularly rodents such as mice) make high frequency noises, so the hearing of the cat has evolved to pinpoint these faint high-pitched sounds. Cats rely more on smell than taste, and have a much better sense of smell than humans.
Cats have a rapid breeding rate. Under controlled breeding, they can be bred and shown as registered pedigree pets, a hobby known ascat fancy. Failure to control the breeding of pet cats by spaying and neutering and the abandonment of former household pets has resulted in large numbers of feral cats worldwide, with a population of up to 60 million of these animals in the United States alone.
As The New York Times wrote in 2007, "Until recently the cat was commonly believed to have been domesticated in ancient Egypt, where it was a cult animal", but a study that year revealed that the lines of descent of all house cats probably run through as few as five self-domesticating African Wildcats (Felis silvestris lybica) c. 8000 BC, in the Near East. The earliest direct evidence of cat domestication is a kitten that was buried alongside a human 9,500 years ago in Cyprus.
The domesticated cat and its closest wild ancestor are both diploid organisms that possess 38 chromosomes and roughly 20,000 genes. About 250 heritable genetic disorders have been identified in cats, many similar to human inborn errors. The high level of similarity among the metabolisms of mammals allows many of these feline diseases to be diagnosed using genetic tests that were originally developed for use in humans, as well as the use of cats in the study of the human diseases.
An interesting example of a mutation that is shared among all felines, including the big cats, is a mutant chemosensor in their taste buds that prevents them from tasting sweetness, which may explain their indifference to fruits, berries, and other sugary foods. In some breeds of catscongenital deafness is very common, with most white cats (but not albinos) being affected, particularly if they also have blue eyes. The genes responsible for this defect are unknown, but the disease is studied in the hope that it may shed light on the causes of hereditary deafness in humans.
Since a large variety of coat patterns exist within the various cat breeds, the cat is an excellent animal to study the coat genetics of hair growth and coloration. Several genes interact to produce cats' hair color and coat patterns. Different combinations of these genes give different phenotypes. For example, the enzyme tyrosinase is needed to produce the dark pigment melanin and Burmese cats have a mutant form that is only active at low temperatures, resulting in color appearing only on the cooler ears, tail and paws. A completely inactive gene for tyrosinase is found in albino cats, which therefore lack all pigment. Hair length is determined by the gene for fibroblast growth factor 5, with inactive copies of this gene causing long hair.
The Cat Genome Project, sponsored by the Laboratory of Genomic Diversity at the U.S. National Cancer Institute Frederick Cancer Research and Development Center in Frederick, Maryland, aims to help the development of the cat as an animal model for human hereditary and infectious diseases, as well as contributing to the understanding of the evolution of mammals. This effort led to the publication in 2007 of an initial draft of the genome of an Abyssinian cat called Cinnamon. The existence of a draft genome has led to the discovery of several cat disease genes, and even allowed the development of cat genetic fingerprinting for use in forensics.
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