v-Ha-ras transgene mRNA expression in Tg.AC mouse skin. Total RNA was isolated and RT-PCR performed on dorsal skin of Tg.AC transgenic mice as previously described. 35 Transgene expression was evaluated at 2, 4, 6, or 8 weeks in mice receiving control (C) or 0.02% sodium-arsenite-treated drinking water (A). MW, molecular weight standard; +, positive control.