Brief historical sketch of chromosomal translocations and tumors.

The discovery of chromosomes emerged from the cytological analysis of mitosis in the 1870s. At the turn of the 20th century, cytologists and geneticists established that chromosomes carried the hereditary material. In the early 20th century, Theodore Boveri, recognizing the nonequivalence of individual chromosomes, began thinking about the biological consequences of imbalances of chromosomal compositions in somatic cells and how these might explain the origin of cancer. Many of his predictions would have to wait for confirmation until the 1950--1960s, when mammalian cytogenetics became feasible with the use of ascites tumors as sources of metaphases. This advance coupled with the discovery of G banding by Caspersson and his associates led to finding characteristic recurring chromosomal abnormalities in certain kinds of tumors. Chromosomal translocations that were associated with promoter deregulations or the formation of novel fusion genes were the prime models. This continuing progress combined with dramatic advances in DNA structure, transcription, and repair have provided new insights into the role of this class of mutations in neoplastic development.