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slug Created with Sketch. Science Questions Why do some dogs have blue eyes?

Why do some dogs have blue eyes?

Like human eyes, dog eyes have a pigment called melanin (MELL-uh-nin) in the iris—the colored part of the eye. The iris has two layers. Brown eyes have melanin in the front and back layers. Lighter eyes have little or no melanin in the front layer and just a little in the back. (If no pigment is in either layer, the iris looks pink.) As an animal develops, genes in its DNA tell its body how much melanin to turn “on” or “off.” This means that animals can have a range of eye colors. The same is true for skin, hair, and fur colors.

There is no blue substance in blue eyes (or green in green eyes). Blue eyes look blue because of the way short light waves bounce around in the iris. The sky looks blue for a similar reason.

Photo by: iStock|cynoclub

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