1994 年 59 巻 4 号 p. 439-444
Until recently, the importance of mitotic crossover between homologous chromosomes and its role in the etiology and evolution of malignancy had not been realized. This was in part secondary to the fact that the only direct evidence for chiasma formation in normal human tissue came from the “pre-banding era.” An actual physical exchange between the chromatids of a homologous pair of chromosomes had not been documented. To date, whatever direct cytogenetic evidence that mitotic crossover exists comes from cancer cells with altered genomes. We report for the first time, demonstration of band to band chromosomal pairing, chiasma formation and chromatid exchange physically visible in normal human blood and amniotic cell culture. With this phenomenon now documented, its role in the malignancy and origin of partial uniparental disomy and consequently in the origin of other hereditary diseases can be relevantly hypothesized.