Isabelline (colour)
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Isabelline, also known as isabella, is a pale grey-yellow, pale fawn, pale cream-brown or parchment colour. It is primarily found in animal coat colouring, particularly plumage colour in birds and, in
Light palomino Quarter Horse, which may be described as isabelline
Isabelline shrike
Mustangs
Leucism
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Leucism or leukism, is a wide variety of conditions that result in partial loss of pigmentation in an animal—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles,
Isabelline (colour)
…well as in other descriptions of birds. The genetic pigmentation disorder isabellinism seen in birds is derived from the colour word and is a form of leucism caused by a uniform reduction in the production and expression of melanin resulting in areas of plumage on the back of the bird, normally black, being…
Leucistic white lions owe their colouring to a recessive allele. Note the eyes and lips remain the normal colour. Studies have shown that the reduced pigment comes from a mutation in the gene for tyrosinase, the same as causes Type I oculocutaneous albinism in humans.
This white horse owes its coloring to a dominant allele (dominant white).
A leucistic rock dove. Both the eyes and legs are still of the normal colour.
A leucistic house sparrow (Passer domesticus) in Kaycee, Wyoming, USA