jan 1, 1959 - 1959: An additional copy of chromosome 21 linked to Down's syndrome

Description:

Today, scientists routinely use our growing understanding of genetics for disease diagnosis and prognosis. However, it took decades for cytogenetics (the study of chromosomes) to be recognised as a medical discipline.

Cytogenetics first had a major impact on disease diagnosis in 1959, when an additional copy of chromosome 21 was linked to Down's syndrome. In the late 1960s and early 70s, stains such as Giemsa were introduced, which bind to chromosomes in a non-uniform fashion, creating bands of light and dark areas. The invention transformed the discipline, making it possible to identify individual chromosomes, as well as sections within chromosomes, and formed the basis of early clinical genetic diagnosis.

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