文档介绍：14 畸变染色体引起的疾病

chromosomal disorder
Any syndrome characterized by malformations or malfunctions in any of the body's systems, and caused by abnormal chromosome number or constitution.
1. Down syndrome
A. A Brief History
The formal story began in 1866, when a physician named John Langdon Down published an essay in England in which he described a set of children mon features who were distinct from other children with mental retardation.
Down was superintendent of an asylum for children with mental retardation in Surrey, England when he made the first distinction between children who were cretins (later to be found to have hypothyroidism) and what he referred to as "Mongoloids."
Down based this unfortunate name on his notion that these children looked like people from Mongolia, who were thought then to have an arrested development.
This ethnic insult came under fire in the early 1960s from Asian ic researchers, and the term was dropped from scientific use. Instead, the condition became called "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 the UK and some places 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 Waardenburg and Bleyer in the 1930s.
But it wasn't until 1959 that Jerome Lejeune and Patricia Jacobs, working independently, first determined the cause to be trisomy (triplication) of the 21st chromosome. Cases of Down syndrome due to translocation and mosaicism were described over the next three years.
B. The Chromosomes
There are three different types of Down syndrome: Standard Trisomy 21, Translocation, and Mosaicism.