But for those of us with them, melanin will tend to cluster in little clumps that darken whenever we spend a day outside in the sun. Freckles aren't permanent, however, and we're not born with them. The less we're exposed to sunlight, the more freckles will fade. Sometimes freckles are confused with other pigmentation conditions called lentigines also known as "liver spots". Unlike freckles, lentigines appear on some people because their skin simply contains more melanocytes, which are the skin cells that produce melanin.
They're also permanent, and won't fluctuate with a person's exposure to UV rays. We also know that freckles are linked to a key genetic determinant for skin and hair color, which is a gene called MC1R.
This particular gene tells our cells how to make a specific protein that's involved in the production of melanin. Stay on top of the latest news with our daily newsletters each morning, lunchtime and evening. Sign up. Sign In. Don't have an account? Forgot Password? Not an Irish Times subscriber? Update Payment Details Not Now. If MC1R doesn't work, you'll get a build up of pheomelanin and end up with red hair. But why does having half your MC1R work sometimes cause freckles? Scientists don't know.
What they know is that having one or two non-working copies of MC1R can sometimes cause freckles. Note the sometimes. Not everyone who is a carrier for red hair has freckles.
So there must be more to freckles than the MC1R gene itself. We haven't yet found what that other thing is. Some recent work also shows that there are other ways to get freckles besides the MC1R gene. Recently a group of scientists in China found another freckle gene. This one was on chromosome 4 in a Chinese family with freckles. So as you can see, we have part of the story on freckles but don't know everything yet. Having broken copies of the MC1R gene isn't always enough. And there are other ways to get freckles besides MC1R.
Most likely we are missing some other genes needed for freckling. Certain versions of these genes might need to be there along with certain versions of MC1R to end up with freckles. Scientists will keep looking. MC1R is a very interesting gene. It leads to the confusing result that freckles are dominant and red hair is recessive. Even though they are the same gene! MC1R alerts the body when exposed to harmful UV radiation is taking place. This is a dominant gene, meaning anyone with at least one copy of the freckle variant from either parent will have freckles.
Some freckles diminish and disappear over time. Others are always present but may fade in winter and be most prominent in summer, when UV exposure is higher. As a general rule, most freckles will tend to last for months or years once they develop. Freckles are not dangerous and do not point to an underlying medical problem. Still, people who have freckles are more susceptible to UV-related skin damage than others. They should wear sunscreen and a hat when out in direct sunlight and minimize sun exposure overall.
Freckles can appear at any time in life for someone with the appropriate gene. In general, freckles are more likely to fade in color as a person ages. Some freckles may disappear entirely. However, new freckles are always possible. Freckles do not denote an underlying health problem. They are just an expression of the MC1R gene.
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