Random segregation of sister chromatids in developing chick retinal cells demonstrated in vivo using the fluorescence plus Giemsa technique

Experiments were designed to test whether nonrandom segregation of sister chromatids at mitosis has a role in the production of cell diversity during embryogenesis. Segregation was examined in vivo in retinal cells from embryonic chicks. Chromatids were labelled with bromouracil and stained by the fluorescence plus Giemsa technique. No evidence of nonrandom segregation was observed in a frequency distribution of pairs of bifilarly labelled sister chromatids at the third metaphase after the start of labelling. Nor was there evidence that chromatids from homologous chromosomes segregated nonrandomly. Nonrandom segregation is probably not a mechanism for cell diversification.