Down syndrome is a chromosomal disorder that produces a set of mental and physical symptoms. It is caused by an extra copy of chromosome 21. In a person with Down syndrome there are three copies of the chromosome 21, one from the father, one from the mother and a third copy. The extra copy of this chromosome changes the development of the brain and body. Down syndrome affects about 1 in every 800 babies. Many people with Down syndrome experience medical problems and learning difficulties and require extensive help to live productive lives.
Discovery of Down syndrome
Down syndrome was first described by a British Doctor named John Langdon Down. He documented the condition in 1887. He called the condition Mongolian type. This is why people with Down syndrome were known as mongoloids. Dr Down could not identify what caused the condition and it was not until 1959 that a Professor named Jérome Lejeune discovered that Down syndrome was caused by a chromosomal irregularity. He found that in people with Down syndrome an extra chromosome was present. Instead of the 46 chromosomes that are commonly found in a person’s DNA, a person with Down’s syndrome had 47. It was later found that this extra chromosome was the cause of the physical and developmental differences in persons with Down syndrome.
In the 1960’s, 18 geneticists campaigned to have the name of Down syndrome changed from “Mongolian idiocy” to “Down syndrome”. Their campaign was successful and in 1965 the WHO (World Health Organization) dropped the previous name and started the use of the term Down syndrome.