In humans each cell contains 23 pairs of chromosome. In excess due to any reason or any deficiency in this number of chromosome results in genetic disorder.
Klinefelter syndrome- Klinefelter syndrome is the presence of an extra X chromosome in a male. According to US National Library of Medicine (A.D.A.M. Medical Encyclopedia) Klinefelter syndrome occurs in about 1 out of 500 - 1,000 newborn boys. Women who get pregnant after age 35 are slightly more likely to have a boy with this syndrome than younger women.
Turner syndrome- The absence of a sex chrosome in the ovaries of a female is termed as Turner syndrome. In some cases, the chromosome is missing in some cells but not others, this is called mosaicism or "Turner mosaicism".
Down's Syndrome - Down syndrome or Down's syndrome, also known as trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866.
Patau syndrome - Patau syndrome, also known as trisomy 13 and trisomy D, is a chromosomal abnormality, a syndrome in which a patient has an additional chromosome 13 due to a nondisjunction of chromosomes during meiosis. The extra chromosome 13 disrupts the normal course of development, causing heart and kidney defects, amongst other features characteristic of Patau syndrome.