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This is an accepted version of this page This is the latest accepted revision, reviewed on 28 December 2024. "Skin pigmentation" redirects here. For animal skin pigmentation, see Biological pigment. Extended Coloured family from South Africa showing some spectrum of human skin coloration Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among ...
Typically, adaptive melanism is heritable: A dominant allele, which is entirely or nearly entirely expressed in the phenotype, is responsible for the excessive amount of melanin. By contrast, adaptive melanism associated with Batesian mimicry in Zelandoperla fenestrata stoneflies is controlled by a recessive allele at the ebony locus. [5] [6]
Leucism (/ ˈ l uː s ɪ z əm,-k ɪ z-/) [2] [3] [4] 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, but not the eyes. [4] It is occasionally spelled leukism.
Autosomal dominant A 50/50 chance of inheritance. Sickle-cell disease is inherited in the autosomal recessive pattern. When both parents have sickle-cell trait (carrier), a child has a 25% chance of sickle-cell disease (red icon), 25% do not carry any sickle-cell alleles (blue icon), and 50% have the heterozygous (carrier) condition. [1]
According to the model of Mendelian inheritance, alleles may be dominant or recessive, one allele is inherited from each parent, and only those who inherit a recessive allele from each parent exhibit the recessive phenotype. Offspring with either one or two copies of the dominant allele will display the dominant phenotype.
The dominant, wild-type A allows hairs to be banded with black and red (revealing the underlying tabby pattern), while the recessive non-agouti or "hypermelanistic" allele, a, causes black pigment production throughout the growth cycle of the hair. [18]
The horse at right lacks the agouti signalling protein, and has a uniformly black or aphaeomelanistic coat. In a chestnut horse, the solid red coat is created by a recessive aeumelanic mutation in MC1R and agouti, if present, is masked. In all cases, the eyes and skin are unaffected.
Light skin is a human skin color that has a low level of eumelanin pigmentation as an adaptation to environments of low UV radiation. [ 1 ] [ 2 ] Due to migrations of people in recent centuries, light-skinned populations today are found all over the world.