mice homozygous for a recessive loss-of-function mutation (m/m) have short tails. gene m is located in a region of chromosome 3 that has 20 genes. to further pinpoint the location of gene m, mice with the point mutation are crossed to six mouse strains that have overlapping deletions in the region. in the diagram, the parentheses define the boundaries of each deletion. the phenotypes of the offspring of the crosses are shown.
