The Genetics of Eye Color

A person's eye color is determined by the genes inherited from their parents. The types of alleles received from the parents are assigned to certain chromosomes. The dominant genes are expressed and the recessive genes are hidden. In the development of the iris those genes tell enzymes to produce and place a certain amount of melanin in the iris to form the eye color.

Eye Color Calculator

1) First, select the Parents' eye colors:   Eye Color of Mother:   Eye Color of Father: 2) Now select the parents' eye color genes: Mother's Genes:   Brown/Blue gene     Green/Blue gene   Father's Genes:   Brown/Blue gene     Green/Blue gene   3) And then:  (press again for more children). Brown eyed Children: Green eyed Children: Blue eyed Children:

So what is going on here?

 

(An explanation for our interactive eye color genetics calculator)

• Eye colors are distinct (brown, green, blue) rather than mixed. If we mixed green and blue paints we would get a greenish-blue paint. Mixing in brown would give mud. Eye colors of children came out as pure green, blue, or brown, not as a mixture of the colors of their parents' eyes.
• Eye color acts like distinct particles are inherited - one can have the particle for green eyes or the particle for blue eyes.
• Children can have different eye colors than either of their parents. This is strange, if colors can't mix. It would make sense if colors mixed and blue and green eyed parents had greenish-blue eyed children.
• Brown tends to swamp out green, green tends to swamp out blue.
• A parent with brown-brown genes produces only children with brown eyes, but a parent with brown-blue eyes could produce children with eye colors other than brown.

Genes are structures that are carried on larger structures called chromosomes. The genes for each characteristic come in pairs, and the two genes together produce a given characteristic. One of the genes of the pair came from the father and the other came from the mother.

An individual with brown and blue alleles of the bey2 gene on chromosome 15. There are two copies of chromosome 15. Each copy has the bey2 gene. On one copy the bey2 gene is in the brown flavor, in the other the bey2 gene is in the blue flavor. The difference between the brown and blue alleles is due to some difference in the genetic code for each gene (the DNA sequence for the bey2 gene isn't yet known).

Genes are particles that get inherited.
Humans have several eye color genes. Two of these genes are named bey2 (brown eye) and gey (green eye).
Genes come in flavors called alleles.
The bey2 gene has two flavors - brown and blue.
The gey gene also has two flavors - green and blue.
Genes are on chromosomes. There is one copy of the gene on each chromosome (some genes also come in many copies).
Chromosomes come in pairs.
Thus each individual has two copies of each gene. These two copies can be the same flavor (allele) or different flavors.

Genes are used to produce proteins. A gene that comes in two flavors might come in one flavor where the protein works correctly and another flavor in which the protein does not work. Thus an individual with one copy of the good flavor and one copy of the defective flavor for a gene could still produce a protein that worked.