Have you ever looked at your child and wondered where all that curly hair came from? Or why only one of your kids seems to be musically inclined? Or why your family photos look like a sea of freckles?
The answer is in your genes – and your environment.
But genetic traits are not as simple as dominant and recessive as most of us learned in high school biology class, according to Joleen Viront, a licensed genetic counselor at Akron Children’s Hospital.
“There are typically multiple genes involved in a singular outcome and when you add the environmental factor on top of that it becomes very hard to pinpoint a reason for something,” she said. “The more we understand about genetics the more we learn we’re not looking for just one gene.”
There are countless combinations of genetic and environmental factors that make each one of us truly unique. But there are basic explanations behind some of the most common observable human characteristics:
- Curly hair – Hair texture is inherited, but the pattern of inheritance is unpredictable and it’s a continuous trait so there’s a gradation of outcomes from straight to curly to wavy hair. Additionally, there are multiple genes involved, which are different across populations – for example, according to the University of Utah Health Sciences, straight hair in Asians is mostly caused by variations in 2 genes, which are different genes from the ones that impact African and European populations.
- Height – You may not guess it but height is determined in part by environment. “As humans, we’ve become taller than we were 100 years ago, mostly due to better diets,” Jolene said. “A person who is genetically predisposed to be tall but is malnourished won’t reach their full height potential.”
- Folding arms and hands – Did you know the way you fold your hands or arms together is in part due to your genes? If you cross your arms, is your right or left arm on top? Or if you clasp your hands together with your fingers interlocked, is your right or left thumb on top?
- Handedness – Preference for using your right or left hand may be determined by up to as many as 100 genes. Environment plays a part, too, with some cultures actively discouraging left-handedness.
The list could go on and on. Some traits like eye color, freckles and dimples are primarily determined through genes while other traits like athleticism, body type and personality can be greatly impacted by a person’s environment.