What The Freck is a Freckle?

I've had freckles all over my body for as long as I can remember- on my face, my arms, my legs, even my back. I always liked my freckles, and I thought they made me cool and unique because no one else had freckles that looked exactly the same as mine. I never really questioned what they were or how they came to be, since most other people in my family and around me also had freckles. I thought they just existed, that I've had them my entire life and it's just apart of my skin. But after having completed the AP Biology course and learning all sorts of different things about cells and the body, I've come to ask myself, what even is a freckle?

Person with freckles. 

What exactly is a freckle?

Freckles are small brown spots that are found on the surface of our skin, and are harmless. Freckles are actually a result of overproduction of melanin in the body, which is responsible for giving us our skin and hair pigmentation. Melanocytes are the cells that are responsible for producing the melanin within our bodies. Sometimes these melanocytes are more clustered together and can overproduce the amount of melanin they make, which leads to smaller, more centralized areas of melanin shown on our skin, which is what a freckle is!

Why do freckles exist?

If you've ever noticed that your freckles are more prominent in the summer than in the winter, there's a good explanation for that. Melanin production is affected by ultraviolet radiation, or UV rays, which come from the sun. Melanin protects the skin from harmful UV rays, as overexposure to UV radiation can cause extreme damage to the skin if the skin is not properly protected, which can lead to damage to the skin barrier and even skin cancer. The sun's UV rays are more powerful and harmful in the summer, which is why it's easier to get a sunburn when you're at the beach, and the reason why your freckles become darker in the summer. So although freckles are harmless, they still serve a purpose, being that they protect your skin from UV damage and make you look pretty unique too.

UV Rays and Melanocytes.

Do I have freckles because my parents have freckles?

Yes! While the appearance of freckles is affected by UV radiation exposure, they are also genetic too! The MC1R gene encodes for a protein called melanocortin 1 receptor. This receptor is responsible for the pigmentation of our skin. Since we inherit two copies of each gene from our mom and our dad, they pass down the phenotypes created from the alleles found on the genes. Having freckles is a dominant trait, so if you have freckles, at least both or one of your parents is homozygous dominant or heterozygous for the dominant allele on MC1R, which is why both you and your parents may have freckles. Then again, your parents may have freckles, but somehow you may not have any freckles at all, which is due to the possibility of both parents being heterozygous (Ff) for the freckle allele. This means that your parents had a 1/4 chance of having a child without freckles (ff), since not having freckles is a recessive trait. The allele for red hair can also be found on the MC1R gene, and is recessive.  It might be confusing that red hair is recessive while freckles are dominant, even though most people with red hair have freckles, but this is because we have two copies of each gene, and the whole process of freckles appearing is the lack of the MC1R gene being able to change one type of melanin into another. So when one copy of this gene does not work, you end up with freckles, and if the other copy also does not work, you end up with red hair too. So while the sun may affect how your freckles appear on your skin, the whole reason they came to exist in the first place is all thanks to your parents. Pretty neat! 

Family Pedigree and the Freckle Allele.

More on Genes and Freckles

All my life, it's been really hard for me to tan. After being at practice outside all day, or hanging out at the beach, I seem to get a little bit of a tan, but nothing crazy compared to some of my friends, who seem to tan so easily. At first I thought maybe it was because I was wearing too much sunscreen, (it's not, don't ever forget to wear sunscreen--there is no such thing as too much) but really it's just because of my genetics. I clearly inherited the dominant allele for freckles on my MC1R genes from my parents, since I have freckles all over my skin. Again, the MC1R gene encodes for a protein that produces melanin. This protein is found on the outside of melanocytes, which are the cells that are also responsible for producing melanin in our skin. When the MC1R protein detects UV rays, it signals to the melanocytes to produce melanin to protect our skin from being damaged. There are different types of melanin that can be produced in our skin- eumelanin and pheomelanin. There are two different types of eumelanin, which is black and brown. This kind of melanin is responsible for dark colors in the skin, hair, and eyes, and when there is little amounts of either eumelanin present, it results in things like blonde hair. Pheomelanin is the type of melanin that gives pigment to our lips, nipples, and other areas of our body that look pinkish. The MC1R protein changes pheomelanin to eumelanin, but the MC1R protein in people who have freckles actually doesn't change the pheomelanin into eumelanin that well, since the melanocytes are more clustered together and have more pheomelanin than usual. Since pheomelanin gives us that pinkish color on parts of our skin, the pigment of pheomelanin is red, which is why freckles have a light orangish color most of the time. 

Location of MC1R Gene on a Chromosome.

So, next time you think you aren't getting a good tan as a person with freckles, but you notice your freckles getting darker, what's really happening is that you are tanning, just in tiny little spots on your skin, which are your freckles. Pretty cool!