Sometimes when meiosis the division of reproductive cells occurs, chromosomes may be lost, left behind, or too many may be passed on, resulting in the birth of a child with a genetic or congenital defect or disease. One of the most common of these genetic disorders is Down syndrome. This disorder takes its name from Dr. Langdon Down, who was the first to describe it formally, in 1866. Down syndrome is a condition marked by abnormal physical and mental development that is caused by a genetic defect. This genetic defect is caused by an extra chromosome. People born with Down...
heart and gastrointestinal defects, control infections with antibiotics, relieve endocrine gland malfunctions, and dental problems can be held in check through early measures against tooth decay, plus orthodontics and restorative dentistry to remedy crooked teeth.

With proper medical care average life expectancy is now almost the same as that of the general population. However, even with excellent nurturing and education, not many Down syndrome adults can be fully independent. Most will always need a protected home and work environment. Institutionalization may still be necessary in a minority of Down syndrome people with incredibly severe physical defects or developmental disability.