Effect of abnormal erythroblast growth on oncogenic ras expression. Expression of oncogenic ras induces abnormal growth of erythroblasts. Purified TER119^- cells were infected with bicistronic retrovirus constructs encoding GFP alone, H-ras wild-type (wt), oncogenic H-ras (H-ras.V12), or dominant-negative H-ras (H-ras.N17) and cultured in fibronectin-coated wells as described in Figure 4. Cell numbers are presented as total viable GFP⁺ cells. Data are averages from triplicate cultures of 2 separate experiments and SDs were always less than 5% of the averages.