One stretch of the gene is repeated a variable number of times, and the version with seven repeats {the "7R" form} produces a receptor protein that is sparse in the cortex and relatively unresponsive to dopamine. This is the variant associated with a host of related traits-sensation and novelty seeking, extroversion, alcoholism, promiscuity, less sensitive parenting, financial risk taking, impulsivity, and, probably most consistently, ADHD {attention-deficit/hyperactivity disorder}.
( Robert M. Sapolsky )
[ Behave: The Biology of Humans ]
www.QuoteSweet.com