If blue eyes are a recessive gene and green eyes are a dominant gene, why are there more people with blue eyes?
In: 151
Eye colour is determined by a single factor – melanin. This is the same pigment that determines human skin and hair colour.
Eyes colour does not come in discrete categories like “blue”, “green, or “brown”, but in a spectrum ranging from pale blue* to dark brown. What we call green is in the middle.
Several genes contribute to eye colour, all by affecting melanin pathways and the regulation of other genes.
So I would guess that “green” eyes are relatively rare because there is a narrow range of melanin concentrations that give that effect, and a small combination of alleles that underlying that.
*Or albino if you lack melanin at all.
Sturm RA, Duffy DL, Zhao ZZ, Leite FP, Stark MS, Hayward NK, Martin NG, Montgomery GW. A single SNP in an evolutionary conserved region within intron 86 of the HERC2 gene determines human blue-brown eye color. Am J Hum Genet. 2008 Feb;82(2):424-31. doi: 10.1016/j.ajhg.2007.11.005. Epub 2008 Jan 24. PubMed: 18252222. Free full-text available from PubMed Central: PMC2427173.
Sturm RA, Larsson M. Genetics of human iris colour and patterns. Pigment Cell Melanoma Res. 2009 Oct;22(5):544-62. doi: 10.1111/j.1755-148X.2009.00606.x. Epub 2009 Jul 8. Review. PubMed: 19619260.
White D, Rabago-Smith M. Genotype-phenotype associations and human eye color. J Hum Genet. 2011 Jan;56(1):5-7. doi: 10.1038/jhg.2010.126. Epub 2010 Oct 14. Review. PubMed: 20944644
Latest Answers