BRAINCAKERed-Green Colour Blindness
Red-green colour blindness is the most common sex-linked condition. People with it find it hard to tell apart reds, greens and colours containing them.
Colour vision depends on cone cells in the retina. There are three types, containing pigments (opsins) most sensitive to red, green or blue light. The genes for the red- and green-sensitive pigments are on the X chromosome. A faulty allele gives an absent or altered pigment, so one type of cone does not work normally.
The condition is X-linked recessive. Using XB for normal vision and Xb for colour blindness:
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Key terms in this lesson
- carrier
- A heterozygous individual who carries a recessive allele for a condition without showing it themselves.
More in Genetic Information
- Gene Linkage
- Identifying Linked Genes
- Chromosome Mapping
- Sex-Linkage
- Pedigree Diagrams
- The Albino Trait
- Sex-Linked Diseases
- Haemophilia
All 30 lessons in Genetic Information · All Edexcel A-level Biology topics