Part 1 of Essay
Down syndrome is a chromosomal abnormality. It is the most frequent form of mental retardation and is characterised by well-defined, distinctive phenotypic features and natural history. An error in cell development results in forty-seven chromosomes rather than the usual forty-six. There are three major types of Down syndr ....

Part 2 of Essay
.... the term was dropped from scientific use. Instead, the condition became "Down's syndrome." In the 1970s, an American revision of scientific terms changed it simply to "Down syndrome," while it still is called "Down's" in Europe. In the first part of the twentieth century, there was much speculation of the cause of Down syndrome. The first people to speculate that it might be due to chromosomal abnormalities were Waardenberg and Bleyer in the 1930s. But it wasn't until 1959 that Jerome Lejeune and Patri ....