Organ-, embryo-, and cell type-associated differences in basal amounts of c-fos transcripts. Data are the numbers of transcript molecules per pg of total RNA. Regarding cultured cells, error bars (SEM) indicate transcript level variability among 13 (NIH 3T3) or 8 (Hepa1-6) independent cultures. Total RNA (pool of ~200 BALB/c mice) from animal organs and whole embryos were from Clontech. No error bars are shown for quantitations of these commercial samples of total RNA. E17 embryos are in late gestation (total of about 19 days). The percentage of c-fos-2 in total transcript amount (c-fos-2 plus spliced c-fos) is indicated for each of the sample examined.