DEFINITION of 'Commercial'. Relating to commerce. In the investment field, the term commercial is generally used to refer to a trading entity engaged in business activities that are hedged by positions in the futures or options markets.
The melanocortin 1 receptor controls which type of melanin is produced by melanocytes. When the receptor is activated, it triggers a series of chemical reactions inside melanocytes that stimulate these cells to make eumelanin. If the receptor is not activated or is blocked, melanocytes make pheomelanin instead of eumelanin.
Skin color is determined by a pigment (melanin) made by specialized cells in the skin (melanocytes). The amount and type of melanin determines a person's skin color. Melanin gives color to the skin, hair, and iris of the eyes. Levels of melanin depend on race and amount of sunlight exposure. Sun exposure increases melanin production to protect the skin against harmful ultraviolet rays. In addition, hormonal changes can affect melanin production.