Cats Mystery

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Genetics

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The domesticated cat and its closest wild ancestor are both diploid organisms that possess 38 chromosomes[42] and roughly 20,000 genes.[43] About 250 heritable genetic disorders have been identified in cats, many similar to human inborn errors.[44] 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 as animal models in the study of the human diseases.[45][46]

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Anatomy

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Domestic cats are similar in size to the other members of the genus Felis, typically weighing between 4–5 kg (8.8–11 lb).[30] However, some breeds, such as the Maine Coon, can occasionally exceed 11 kg (25 lb). Conversely, very small cats (less than 1.8 kg (4.0 lb)) have been reported.[47] The world record for the largest cat is 21.3 kg (47 lb).[48] The smallest adult cat ever officially recorded weighed around 1.36 kg (3.0 lb).[48] Feral cats tend to be lighter as they have more limited access to food than house cats. In the Boston area, the average feral adult male will scale 3.9 kg (8.6 lb) and average feral female 3.3 kg (7.3 lb).[49] Cats average about 23–25 cm (9–10 in) in height and 46 cm (18.1 in) in head/body length (males being larger than females), with tails averaging 30 cm (11.8 in) in length.[50]

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Senses

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Cats have excellent night vision and can see at only one-sixth the light level required for human vision.[53]:43 This is partly the result of cat eyes having a tapetum lucidum, which reflects any light that passes through the retina back into the eye, thereby increasing the eye's sensitivity to dim light.[72] Another adaptation to dim light is the large pupils of cats' eyes. Unlike some big cats, such as tigers, domestic cats have slit pupils.[73] These slit pupils can focus bright light without chromatic aberration, and are needed since the domestic cat's pupils are much larger, relative to their eyes, than the pupils of the big cats.[73] Indeed, at low light levels a cat's pupils will expand to cover most of the exposed surface of its eyes.[74] However, domestic cats have rather poor color vision and (like most non-primate mammals) have only two types of cones, optimized for sensitivity to blue and yellowish green; they have limited ability to distinguish between red and green,[75] although they can achieve this in some conditions.[76][clarification needed]