Abstract
1. F_1 female mice obtained from the cross between C57BL females (+/+) and MC males (mic/mic) were backcrossed to MC males or to C57BL males. Half of pregnant females were treated with trypan blue on day 7 of pregnancy. F_1 male mice obtained from the cross between C57BL females and MC males were backcrossed to MC females. The offspring were examined for eye abnormalities on day 18 of gestation. 2. When F_1 females were backcrossed to MC males, the incidence of microphthalmia was lower than expected from the genotype, and when the females were treated with trypan blue, the incidence increased as expected. When F_1 females were backcrossed to C57BL males, there was no difference in the incidence of microphthalmia between the trypan blue-treated and untreated groups. When F_1 males were backcrossed to MC females, the incidence of microphthalmia was as expected. 3. Trypan blue treatment increased the incidence of microphthalmia, suggesting a combined action of trypan blue and mic gene. The maternal genotype also influenced the manifestation of mic microphthalmia.
