Ask A Scientist
Why are some animals albino?
Asked by: Madeline McCarthy
School: Maine-Endwell Middle School
Teacher: Kevin Wagstaff
Hobbies/Interests: Drawing and cleaning
Career Interest: Architect, artist, astronomer or animal rescue person
Answer from Celia Grace Murnock
Graduate Student in Biomedical Anthropology, Binghamton University
Research area: Lyme disease ecology
Interests/hobbies: Reading, baking and traveling
In order to talk about what happens to produce an albino animal, first we need to take a look at what gives animals color in the first place. Much of the color variation that we see in nature is the result of pigments, which are substances that absorb some colors and reflect others.
According to a "Causes of Color" reference found on webexhibits.org, "Pigments are chemical compounds responsible for color in a range of living substances and in the inorganic world." Plants and animals both produce several different pigments. For instance, chlorophyll is a green pigment.
In humans, the pigment hemoglobin causes our blood to appear red, and a purple pigment called rhodopsin, found in the eye, helps us see in dim light. One of the most important groups of pigments is called melanin. There are several types, but for this discussion we will talk about the group as a whole.
Melanin has several functions within the body. In the skin of humans and other animals without protective fur, melanin helps protect against harmful ultraviolent (UV) radiation. The wide range of skin tones you see in people is a result of different levels of melanin. In many species, melanin helps animals camouflage themselves in earth-toned surroundings. Melanin is also found in the eye, not only in the iris, where we see color, but also in the retina, where it plays a role in vision.
An animal or person with albinism (an albino) produces little or no melanin, which is why they are often (but not always!) very pale. Because of the lack of melanin in the eyes, animals with albinism generally have poor vision. In fact, a human is usually diagnosed with albinism based not on complexion, but on a vision test.
There are several gene mutations that can affect an animal’s ability to produce melanin. These mutations are usually autosomal, meaning that they are not found on X or Y chromosomes. They are also usually recessive, meaning that an animal would have to get a copy of the gene from each parent in order to be affected. However, though it is rare, there are a few circumstances where a genetic variant for albinism may be either sex-linked or dominant.