<unk>  is the state of having two types of functioning color receptors, called cone cells, in the eyes. Organisms with<unk>  are called dichromats. Dichromats can match any color they see with a mixture of no more than two pure spectral lights. By comparison, trichromats can perceive colors made of up to three pure spectral lights, and tetrachromats can perceive colors made of four.<unk>  in humans is a color vision defect in which one of the three basic color mechanisms is absent or not functioning. It is hereditary and sex-linked, predominantly affecting males.<unk>  occurs when one of the cone pigments is missing and color is reduced to two dimensions. The term is from di meaning "two" and chroma meaning "color".
Dichromacy
Consanguinity
Heredity
Chromosomal fragile site
Genetic predisposition
Nuclear sexing
Sex linkage
Premorbidity