History of Down’s syndrome

In 1866, the British doctor John Langdon Down discovered the genetic disorder. He called it “Mongolism.” Although, the condition afflicts all races and ethnicities without exceptions.

In 1959, the French Geneticist Professor Jerome Lejeune discovered that Down’s syndrome happens because of an extra chromosome. During the early 1970’s it became known as “Down’s syndrome,” and more research confirmed Professor Lejeune’s findings.

What is Down syndrome

Down’s syndrome (or Trisomy 21) is a glitch in the genetic makeup of human beings. When a man and a woman meet to make a baby, each of them contributes half the DNA of the child.

The normal DNA has 46 chromosomes, 23 chromosomes provided by each parent. But, the person with Down syndrome has one extra chromosome. The chromosome pair 21 gets one extra chromosome, so instead of two, they have three or damaged chromosomes. That’s why it is also called Trisomy 21.


It is the flawed cell division process which causes the Down’s syndrome. Because when it happens, sperm or an egg cell is left with an extra copy of chromosome before or during conception. Nondisjunction is responsible for 95 percent of Down’s syndrome cases.

The other 5 percent of Down syndrome are due to conditions called mosaicism and translocation. Mosaic Down syndrome occurs when some cells are normal while others have Trisomy 21.

Quick Facts on Down syndrome

  • The older the woman gets (35 and above) the more likely it is for the baby to be born with Down syndrome.
  • It is possible to detect Down syndrome in the fetus before it is born through a set of screening tests.
  • Chromosome 21 damage is the primary cause of Down syndrome. A less common form of Down syndrome, mosaicism, occurs when the damage is in other chromosomes. However, the exact reason for this abnormality is unknown.
  • The characteristics of Down syndrome include weak muscles, short height, flat nasal bridge, and a protruding tongue.
  • More than 400,000 people in the United States are living with Down syndrome.

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