In Drosophila, the variegated phenotype of the white mottled allele is suppressed by a dominant autosomal mutation that knocks out the function of the gene for heterochromatin protein 1 (HP1), an important factor in heterochromatin formation. Flies with the white mottled allele and the suppressor mutation have an almost uniform red color in their eyes; without the suppressor mutation, the eyes are mosaics of red and white tissue. Can you suggest an explanation for the effect of the suppressor mutation?