FIGURE 2.

Non-random segregation of radioactive chromosomes in primary cultures of mouse embryo cells (data taken from Figures 1 and 2 of Lark et al., 1966). Distribution of silver grains in autoradiographs of mouse embryo cells: (I) Grown as a primary tissue culture for 1, 2, or 3 generations in H3-thymidine (0.025 mc/ml). (A) An inoculum of 2.5 × 10⁶ cells per Petri dish (100 mm) was grown for 24 h. (B) 1.25 × 10⁶ cells were grown for 48 h. (C) 0.63 × 10⁶ cells were grown for 72 h. (II) Grown as a primary tissue culture for one generation in H3-thymidine (0.025 mc/ml) and for two subsequent generations in non-radioactive medium (chase). (A) 0.3 × 10⁶ cells per Petri dish (35 mm) were grown for 24 h, in medium containing H3-thymidine; (B) 0.15 × 10⁶ cells were grown for 24 h as in (A), and then the medium was replaced with non-radioactive medium and cells grown for an additional 24 h; (C) 0.08 × 10⁶ cells were grown for 24 h as in (A) and then for 48 h in non-radioactive medium. For details see Lark et al. (1966). The solid curves represent the result expected under a null hypothesis of random segregation of equally labeled chromosomes.