What is the difference between skin color and eye color in how the phenotype is expressed?

Answer 1

Hi! Great question.

While skin color and eye color have similarities in the sheer variety of genes that can combine in endless ways to create certain phenotypes for each trait, I have delineated some differences below:

1. due to the increased surface area, skin color can be different in different areas of the body, due to environmental, immunologic, and genetic factors. This is seen with conditions such as vitiligo.
2. Skin color can change throughout your life as certain medications or illnesses can lead to hyper- or hypo- pigmentation in different parts of the skin
3. Eye color has a smaller surface area, leading to the main color primarily being one of select few. However, eye color is unique in that heterochromia can lead to two different eye colors, one for each eye.
4. The main distinction in eye color boils down to how much of a color is seen in a person's eye. For example, one person's eyes can have higher concentrations of blue than brown while another person can have equal amounts of green and gray.