The house mouse, Mus musculus, harbours a variable
cluster of long-range repeats in chromosome
1. As shown in previous studies, some high-copy clusters such as the MUT
cluster are
cytogenetically apparent as a homogeneously staining region (HSR) and are
associated with a
distortion of the Mendelian recovery ratio when transmitted by heterozygous
females. The effect is
caused by a decreased viability of +/+ embryos. It is compensated by
maternal or paternal
MUT. In this study, a deletion derivative of MUT,
MUTdel, shows normal transmission ratios and
no compensating capability. In this respect, MUTdel
behaves like a wild-type cluster. Hence, both
properties – transmission ratio distortion and compensating capability
–
map to the deleted region.
The deletion comprises three-quarters of the MUT HSR and does
not extend to the nearest
markers adjacent to the HSR.