In the Genes: Where Baby's Looks Come From

Whoa, Who Knew?

Some surprising facts about human DNA.

  • Red hair is one of the few traits controlled by a single gene; if Baby gets two copies, she'll produce lots of pheomelanin and have fiery locks. She'll also get light skin and freckles; the same gene causes the skin's melanocytes to clump rather than distribute evenly. (Got freckles but not red hair? You may have inherited only one copy of the ginger gene.)
  • You can pass along the quirky way you furrow your brow while thinking. Expressions may be hereditary. A study in Evolution found that people who are born blind are far more likely to share their relatives' (rather than strangers') exact facial expressions for concentration, anger, disgust, joy, surprise, and sadness. The blind participants didn't learn to make these faces by watching relatives, so the results suggest a genetic link.
  • If your son eventually loses his hair, you may not be to blame. Despite conventional wisdom, genes for male-pattern baldness can be inherited from either parent. It's not only moms who hand them down. Scientists have discovered multiple genes that can play a role in hair loss.
  • You might have been taught that the ability to roll your tongue is a simple genetic trait, controlled by one gene with two alleles. (Same goes for having dimples, a chin cleft, or attached earlobes.) It was once thought that if, say, you inherited a dominant copy of the tongue-roll gene from one parent that turns the trait on, you would be able to do this party trick. But the reality is more complicated. For example, studies show that identical twins don't always share the tongue-rolling quirk. How odd!

Originally published in the March 2012 issue of American Baby magazine.

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