in Heredity and Variation by

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  1. It causes due to the presence of an extra copy of chromosome 21.
  2. Therefore, there are 3 chromosome 21 that is called as trisomy 21.
  3. This extra chromosome causes problem in body and mind development.


  1. The symptoms vary from person to person depends on the severity of disorder.
  2. The symptoms of children with Down syndrome can easily recognized.
  3. They are having smaller head with abnormal shape, e.g.: head may be round but it might be flat from back.
  4. The inner corner of eyes might be having curves rather than points.
  5. Children may also have delayed mental and social development.
    1. Impulsive behavior
    2. Poor judgment
    3. Short attention span
    4. Slow learning
  6. Following are some common symptoms:
    1. Decreased muscle tone at birth
    2. Excess skin at the nape of the neck
    3. Flattened nose
    4. Separated joints between the bones of the skull (sutures)
    5. Single crease in the palm of the hand
    6. Small ears
    7. Small mouth
    8. Upward slanting eyes
    9. Wide, short hands with short fingers
    10. White spots on the colored part of the eye (Brushfield spots)
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