How many genes responsible for eye color

As Dr. Fan Liu et al. Eye color and the prediction of complex phenotypes from genotypes. Current Biology 19 5 : R—R Richard A. Sturm et al. Genetics of human iris colour and patterns. Pigment Cell Melanoma Res. It is not a substitute for professional medical advice, diagnosis or treatment. Never stop or delay seeking treatment because of something you have read on the GB HealthWatch website.

The combined efforts of these genes may boost melanin levels to produce hazel or brown eyes, or reduce total melanin resulting in blue eyes. This explains how two parents with blue eyes can have green- or brown-eyed children an impossible situation under the Davenport single gene model — the combination of color alleles received by the child resulted in a greater amount of melanin than either parent individually possessed.

As a side note, while there is a wide variability in eye color, colors other than brown only exist among individuals of European descent. African and Asian populations are typically brown-eyed. In a team of researchers studying the OCA2 gene published results demonstrating that the allele associated with blue eyes occurred only within the last 6, — 10, years within the European population. Pigmentation research at HudsonAlpha Dr.

Greg Barsh, a physician-scientist who has recently joined the HudsonAlpha faculty, and his lab study key aspects of cell signaling and natural variation as a means to better understand, diagnose and treat human diseases. In particular, his work has focused on pigmentation disorders.

He has explored mutations that affect easily observable traits—such as variation in eye, hair or skin colors—as a signpost for more complex processes such as diabetes, obesity, neurodegeneration and melanoma, the most serious form of skin cancer. Several disorders that affect eye color have been described.

Ocular albinism is characterized by severely reduced pigmentation of the iris, which causes very light-colored eyes and significant problems with vision. Another condition called oculocutaneous albinism affects the pigmentation of the skin and hair in addition to the eyes.

Affected individuals tend to have very light-colored irises, fair skin, and white or light-colored hair. Both ocular albinism and oculocutaneous albinism result from mutations in genes involved in the production and storage of melanin. Another condition called heterochromia is characterized by different-colored eyes in the same individual.

Heterochromia can be caused by genetic changes or by a problem during eye development, or it can be acquired as a result of a disease or injury to the eye. Am J Hum Genet. Epub Jan PubMed: Sturm RA, Larsson M. Genetics of human iris colour and patterns. Pigment Cell Melanoma Res. Epub Jul 8. Each chromosome that you cut out should have two of the same letters one capital and one lower case on the top and the two same numbers on the bottom.

Do not cut along the line in between two similar numbers! Be careful not to cut yourself when using the scissors. Fold along the line separating each of the letters and numbers so that one letter and one number are visible on either side when the piece of paper is folded. Place a piece of tape in between the letters and numbers so that the piece of paper remains folded in half.

Take all 23 male chromosomes and all 23 female chromosomes and place them into a box or large bowl. Shake the chromosomes so that they mix well. Raise the chromosomes above your head and spill them out onto the floor.

Without flipping any of the chromosomes over, line up chromosomes of the same number beside one another. You will have one male and one female chromosome for each number from one to twenty-three, thus giving you 23 pairs of chromosomes. The letters on each of the chromosomes will be your genotype. These letters each represent a gene.

Remember that capital letters represent dominant genes and lower case letters represent recessive genes. Before finding any physical features, look at the pair of chromosomes with a number Chromosome 23 determines the gender of your individual.

Using the genotype conversion chart, find out if your individual is male or female. According to the chart, if the two letters facing up are X and X, your individual will be female. If the two letters facing up are X and Y, your individual will be male. Now look at chromosome 1, and refer to the genotype conversion table. As the chart indicates, chromosome 1 determines head shape.

The two letters on chromosome 1 represent the genotype. If the letters facing up are S and S or S and s, the head shape will be oval. If the letters facing up are s and s, the head shape will be round. Using a pencil, sketch the head shape that your genotype indicates.