Phenotypes and Genotypes for human eye colors
Part of the study of genetics involves being able to predict the appearance (phenotype) and genetics (genotype) of the offspring of animals or people. Sometimes this is just for fun, such as breeding dogs to get a certain color, but sometimes it is very serious, as when dealing with diseases that can be passed from parents to their children. Here is an example of what we know about the genetics of eye color.
There are three known human eye color genes named: EYCL1 (gey), the Green/blue eye color gene, located on chromosome 19. EYCL2 (bey1), the central brown eye color gene, possibly located on chromosome 15. EYCL3 (bey2), the Brown/blue eye color gene located on chromosome 15. A role has also been suggested for the Melanocortin Receptor Gene (MCIR) on chromosome 16. A second gene for green has also been postulated. Other eye colors including black, grey, and hazel are not yet explained. We do not yet know what these genes make (except MCIR), or how they produce eye colors. The two gene model (EYCL1 and EYCL3) used here clearly does not explain more than a portion of human eye color inheritance.
Two gene model: There are two genes involved in eye color. One gene has Dominant Brown or recessive blue states, the other has Dominant Green or recessive blue states. We further assume that Brown in the first gene will swamp out Green or blue from the second gene, and Green from the second gene will swamp out blue from the first gene. Because chromosomes come in duplicate pairs, each parent has two copies of each gene.
Phenotypes and Genotypes for human eye colors
Possible Phenotypes and Genotypes under the two gene model
Phenotype: Blue Eyes
1 Possible Genotype:
Gene: bey2 Gene: gey
Chromosome 15 Copy 1: blue
Chromosome 15 Copy 2: blue Chromosome 19 Copy 1: blue
Chromosome 19 Copy 2: blue
Phenotype: Green Eyes
2 Possible Genotypes:
Gene: bey2 Gene: gey
Chromosome 15 Copy 1: blue
Chromosome 15 Copy 2: blue Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: Green
Chromosome 15 Copy 1: blue
Chromosome 15 Copy 2: blue Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: blue
Phenotype: Brown Eyes
6 Possible Genotypes:
Gene: bey2 Gene: gey
Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: Brown Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: Green
Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: Brown Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: blue
Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: Brown Chromosome 19 Copy 1: blue
Chromosome 19 Copy 2: blue
Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: blue Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: Green
Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: blue Chromosome 19 Copy 1: Green
Chromosome 19 Copy 2: blue
Chromosome 15 Copy 1: Brown
Chromosome 15 Copy 2: blue Chromosome 19 Copy 1: blue
Chromosome 19 Copy 2: blue
http://www.athro.com/evo/gen/eyecols.html
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