What does modal eye colour mean?

Modal eye colour refers to the most frequently occurring eye colour in a given population. For example, in the United States, the modal eye colour is brown. This simply means that brown eyes are more common in the US than any other eye colour.

Eye colour is determined by the amount and distribution of melanin in the iris. Melanin is a pigment that also gives skin and hair their colour. People with more melanin tend to have darker eyes, while people with less melanin tend to have lighter eyes.

There are many different factors that can affect eye colour, including genetics, ethnicity, and environmental factors such as sun exposure. However, genetics plays the most important role in determining eye colour.

The genes for eye colour are located on chromosome 15. There are two main genes that determine eye colour: the OCA2 gene and the HERC2 gene. The OCA2 gene codes for a protein that is involved in the production of melanin. The HERC2 gene codes for a protein that is involved in the regulation of the OCA2 gene.

Variations in these genes can lead to different eye colours. For example, people with two copies of the brown-eyed allele (OCA2-B) will have brown eyes. People with one copy of the brown-eyed allele (OCA2-B) and one copy of the blue-eyed allele (OCA2-b) will have hazel or green eyes. And people with two copies of the blue-eyed allele (OCA2-b) will have blue eyes.

In addition to genetics, other factors such as ethnicity and environmental factors can also affect eye colour. For example, people of African descent tend to have darker eyes than people of European descent. And people who live in sunny climates tend to have lighter eyes than people who live in cloudy climates.

Modal eye colour is simply the most frequently occurring eye colour in a given population. It is determined by a combination of genetic, ethnic, and environmental factors.