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There's no specific skin gene, but genetics obviously play a big role in determining your skin tone and type.

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Your skin is affected by numerous external factors, such as your environment or your skin care routine. Underneath the surface, your skin is affected by a more permanent factor: your genes.

In general, genes, which are made of DNA, determine all the different characteristics of a living thing. They do this by telling your cells how to make proteins, which in turn affects all the structures and functions in your body. Scientists estimate that humans have between 20,000 and 25,000 different genes [source: Genetics Home Reference].

Genetics are complicated by the fact that there is no specific skin gene -- many genes work together to affect a single trait, and many traits can be affected by a single gene. Genes have a significant influence on skin because skin is made of so many proteins. For example, collagen, which forms the basic structure of your skin and gives it strength, is a protein. So is melanin, which is the pigment that gives your skin its color.

Often, genetic factors are thought of in terms of heredity -- that is, if your parents have a certain trait, you're likely to have it. This is at least partially true for many skin-related characteristics, such as skin type and skin color. However, it's not easy to definitively isolate genes that cause skin color. Many researchers have tried to determine which specific genes are linked to skin color and skin type, but more studies still need to be done because so many factors, both genetic and environmental, affect these traits [source: Barsh, Matulef].

So you now know that genes affect the normal characteristics of your skin, but what happens when genes behave in abnormal ways? Read on to find out how genetic disorders can affect the skin.