In 1866, an Englishman, named John Langdon Down, published the first clinical description of the condition that is now called Down syndrome (Capone 2004). According to Turner & Alborz (2003), Down's syndrome occurs in approximately one in six hundred live births per year. Also known as Trisomy 21, Down syndrome is a common birth defect caused by an error in cell division. This error in cell division causes the person to have an extra portion on the number 21 chromosome present in all, or some, of their cells. …
