Righty or Lefty: is dominant hand influenced by genetics?
Handedness is a trait that appears to be influenced by multiple factors, such as environment, chance, and also genetics.
Handedness is the individual preference for use of a hand, called dominant hand. The less preferred hand is called the non-dominant hand.
About 90% of the world’s population is right-handed, making right-handedness the most common form. Handedness is often defined by which hand one writes with, as it is fairly common for people to prefer to do some tasks with each hand. Even though there is some true mixed-handedness, it is very rare since most people prefer one hand for most purposes.
Hand preference begins to develop before birth and it becomes increasingly apparent in early childhood tending to be consistent throughout life. But what about its biological basis? It probably arises as part of the developmental process that differentiates the right and left sides of the body (called right-left asymmetry). Handedness appears to be related to differences between the right and left halves (hemispheres) of the brain. The right hemisphere controls movement on the left side of the body, the left hemisphere controls movement on the right side of the body.
Initially, it was thought that a single gene controlled handedness, but recent studies found that multiple genes, maybe up to 40, contribute to it. Those genes all together play a significant role in establishing hand preference.
For example, the PCSK6 gene has been associated with an increased likelihood of being right-handed in people with the psychiatric disorder schizophrenia. Gene LRRTM1 has been associated with an increased chance of being left-handed in people with dyslexia. It is unclear whether either of these genes is related to handedness in people without these conditions.
Also, other factors contribute to handedness such as the prenatal environment and cultural influences.
Handedness does not have a simple pattern of inheritance, as happens with many complex traits. Children of left-handed parents are more likely to be left-handed than are children of right-handed parents. However, because the overall chance of being left-handed is relatively low, most children of left-handed parents are right-handed. Identical twins are more likely than siblings to be either right-handed or left-handed, but many twins have opposite hand preferences.