Duchenne muscular dystrophy (dmd) is normally an x-linked recessive human disease affecting boys. girls afflicted with dmd are rare. cytogenetic studies of several girls with dmd have in each case revealed that these individuals carry x-autosome translocations. the autosomes vary, but the breakpoint on the x in every case is in band p21, which is the location of the dmd gene. cytogenetic studies further revealed that in all cells studied in such dmd girls the normal x chromosome exists as a barr body. how might these observations account for the existence of dmd-affected girls?
(a)- inactivation of the normal x chromosome in all cells of these females eliminates wild-type dmd gene activity.
(b)-these dmd girls are heterozygous for a wild-type allele and a disrupted dmd gene.
(c)-the translocation breakpoint likely falls in or near the wild-type dmd gene.
(d)-all of the above