Skin color determination is an issue that has fascinated many people for a long time. It is by understanding of some of the factors that influence skin color that we can then find ways of modifying it without posing a risk to our health. Fortunately, science has come far enough to have very good understanding of the factors that determine skin color that an individual will have.
Melanin Plays a Key Role
The most direct answer about what determines skin color is melanin. Melanin is a protein product made by the cells of the skin within the lower layers of dermis. This protein is then transported and deposited within the upper layers of the skin. People who have more melanin tend to have darker skin compared to those who have less melanin.
In addition to skin, melanin is also responsible for coloring of eyes and hair. Evolutionarily speaking, this mechanism is used to protect the body against UV radiation from the sun, since melanin absorbs most of it before it reaches the deeper layers of the skin. This is why people who live around the tropics, where much of the melanin from the sun is deposited, have more melanin compared to those in other regions where sunlight is rarer and therefore UV exposure much less.
In the human body, everything that is controlled by proteins is controlled by genes, since it is the genes which encode the proteins. This case applies for melanin as well. There are two ways in which skin color can be affected by genetics. One, if the genes responsible for formation of an enzyme known as tyrosinase are defective, then lower amounts of this enzyme are formed and this means that no melanin is formed. This is because this enzyme is they key final step in transforming tyrosin to melanin, so its absence results in skin that has no melanin at all. This will manifest as abnormally white skin, as in albinism.
These genes can be transferred from parent to child, and in some cases the mutation that occurs leading to the modification can occur in vitro. This would manifest as two couples with adequate melanin giving birth to a child who can produce very little or no melanin.
The intake of some drugs can influence one’s skin color. For instance, some drugs will increase the activity of tyrosinase enzyme as a side effect, and this will result as an increase in melanin production. This manifests as the individual growing darker when use of the drug is sustained for a long time. Such side effects are usually well-studied, so you are likely to be told about them before starting to use a drug in the long term.
There are some diseases which can be acquired in life which lead to a change in skin pigmentation. One of the commonest of these is vitiligo. In this disease, an individual develops white patches on their skin, and these could grow with time. These patches are more prominent in people with darker skin, and can grow to cover the entire body.