EXPRESSION OF THE MUTANT-GENE MI IN MICE - WHITE SPOTTING PATTERN

Mice of mi/+ and +/+ genotypes of the mutant stock microphthalmia (mi) were mated inter se and with those of CC57BR/Mv and CBA/J inbred line s. In all types of crosses, the offsprings of mi/+ genotype had unpigm ented fingers and distal tail parts (penetrance 100%). This trait is d etermined mostly by the mutant mi gene, the expression of which is not affected by modifier genes. However, the degree of mi gene expression , white spotting, on other body parts (wrist, foot, ventral body side, and parietal head part) varied widely in mice obtained from different crosses; penetrance ranged from 0 to 100%. The results obtained indic ate that in these cases, the expression of mi gene was strongly affect ed by modifier genes. The different frequency of the mi gene effects, in heterozygote offspring obtained from reciprocal crosses. Can result from the imprinting of the modifier genes in maternal and paternal ga metes.