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Determining Eye Color
 Eye color is determined by the amount of a pigment called melanin that is present there in the iris of the eye. Now, how much this amount is, is determined by the genes controlling pigment production. Brown eyes have a good amount of this pigment, whereas blue eyes have less of it. The cell nucleus comprises 46 chromosomes in 23 pairs of two each, one coming from each parent.  A gene is a length of DNA on a chromosome, it (the gene) being the basic unit of heredity. Genes are arranged in the forms of alleles.  A person carrying two of the same alleles goes homozygous for that gene.  If alleles are different, the person goes heterozygous for that gene and one allele goes dominant over the other which goes recessive, i.e., not expressing itself.  In incomplete dominance, the expression goes intermediate between the two alleles.  In co-dominance, both alleles express themselves fully and simultaneously, e.g., blood group AB coming from allele A and allele B in their total expression simultaneously.  Eye color does not follow the simple dominant/recessive inheritance pattern of a single gene pair. There are three gene pairs that control the human eye color. Two of them are there on chromosome pair 15 and one, on chromosome pair 19. The bey 2 gene, on chromosome 15, has a brown and a blue allele. 
The gey gene, on chromosome 19 has a blue and a green allele. 
The bey 1 gene, on chromosome 15, has a brown eye color allele.  Now, how they exactly interact with one another; through recessing, dominating, expressing themselves midway, or simultaneously full together; is not absolutely clear yet.  It seems there are some missing links yet to be discovered in order to understand the exact pattern of the eye color inheritance to be determined genetically. The color genes produce enzymes which decide for the amount of melanin in the iris. At the physiological and the anatomical level, the color of the eye is determined by the amount of a dark brown pigment - named melanin - present in the iris of the eye. 
If the amount is much, the eye goes brown or even black. If the amount is scarce, the eye turns blue. With in-between amounts, the eye color may go gray, green, hazel or some lighter shades of brown. If the amount is nil, the eye takes its hue from the blood vessels in the back of the eye and appears to be pink. Albinos are the example of this. I invite you to subscribe to my weekly E-zine titled Third Eye-zine. This weekly E-zine publishes rare, revolutionary articles which are of real use in the day-to-day life of a common man, covering topics concerning the effect of third eye opening on health, diseases, personality, performance, efficiency, relationship, sex, mind, creativity, passion, business, management, and energy level of a person; apart from its effect on vision correction. A not-to-be-missed opportunity! Subscribe to it here: I also invite you to subscribe to my Third Eye Blog - no need to provide your e-mail address here. This RSS feed keeps you informed about new developments taking place on this site. It also harbors my weekly Third Eye Bloglet narrating My Story : My Date with My Body - a bloglet about vision, mind, sex, science, and society. A real interesting reading! In order to subscribe to the blog, right-click on the orange RSS button (see buttons up to the left) and then paste the URL into your RSS reader. Or click on add to My Yahoo! button or My MSN or Add To Google button if you keep a personalized home page there. If you are not sure what RSS or blogging is all about, click on What's an RSS Feed? here:
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