Reduced penetrance and variable expressivity are factors that influence the effects of particular genetic changes. These factors usually affect disorders that have an autosomal dominant pattern of inheritance, although they are occasionally seen in disorders with an autosomal recessive inheritance pattern.enetrance refers to the proportion of people with a particular genetic change (such as a mutation in a specific gene) who exhibit signs and symptoms of a genetic disorder. If some people with the mutation do not develop features of the disorder, the condition is said to have reduced (or incomplete) penetrance.
Although men have more muscle mass than women, both sexes reach their physical peak as young adults or anywhere from their late 20's to early 30's, according to âHuman Development: A Life-Span Viewâ by Robert Kail and John Cavanaugh.
Men grow extremely fast between the ages of 11-15, and during this growth spurt the increase in height can be as much as 12 inches (30cm). After the age of 16 the increase in height is more gradual and boys usually stop growing between the ages of 17-20. So the majority of guys will reach their final height and stop growing when they are around 20 years old. During this growth phase, feet, hands, legs, and muscles start to grow. A manâs shoulders will also broaden and boys start to grow hair on their hands, legs, armpits, and chest.