Not all redheads have freckles as some redheads have milk white skin.
The connection between red hair and freckles is that they are both caused by the MC1R gene. This gene is basically responsible for the production of the MC1R protein, which is involved in the distribution of pigments in hair and skin. Two main pigments affect people’s hair and skin, eumelanin and pheomelanin. People with freckles and red hair have more pheomelanin than people with other hair colors and skin without freckles. The basic reason for this is that the MC1R gene works, in this case it converts pheomelanin to eumelanin, or it doesn’t, which results in an accumulation of pheomelanin.
The MC1R gene causes red hair and freckles.
Genetics is basically the study of how traits in genes are passed from parents to children. Each child receives two copies of each gene, one from the mother and one from the father. Variations in things like hair and eye color are related to genetics and can be explained through the different versions of each gene that can be inherited from parents. Red hair and freckles can be caused by one version of the same gene, so people with that version of the gene are more likely to develop these traits.
Variations in things like hair and eye color are related to genetics.
Understanding the function of the MC1R gene is important to understanding the connection between red hair and freckles. Basically, the gene tells the body how to make the MC1R protein, which is responsible for controlling skin pigments. Pigments are different chemicals that control skin color, with eumelanin and pheomelanin being the two main ones. Pheomelanin is much rarer, and most people with an active MC1R gene convert it to eumelanin, which causes most people to have hair colors other than red. If the gene is not working properly, pheomelanin builds up, causing red hair and freckles.
Freckles are the result of unevenly distributed melanocyte cells under the skin.
Freckles are caused by an uneven distribution of melanocyte cells in the skin. Most people have lost melanocytes, which create the pigment responsible for changing skin color when exposed to the sun. People with a variety of melanocytes tan evenly, but people with clusters of melanocytes end up with concentrated patches of different colors called freckles. The MC1R gene can also cause melanocyte cells to clump together in this way. This is why people with damaged MC1R genes often have red hair and freckles.
The reason some people have red hair without freckles or freckles without red hair is that they get two copies of each gene, one from their mother and one from their father. If only one gene is broken, the person may have clusters of melanocytes but not excess pheomelanin. In cases where both are broken, the person will be left with red hair and freckles.