Developmental regulation of the globin BAC transgene. Timed matings were performed between transgenic F₁ male mice from line no. 1 and WT B6/C3H female mice. RNA was harvested on e10.5 (yolk sac), e14.5 (fetal liver), e18.5 (fetal liver), or from adult mice >6 weeks old (peripheral blood). Multiplex RT-PCR was performed to determine the relative levels of human ɛ-, γ-, or β-globin mRNA at different stages of development. (•) Human ɛ-globin mRNA; (▴) human γ-globin mRNA; (▪) human β-globin mRNA. Each data point represents an average value for several experiments.