Eliminates crossing over in chromosome 3 except at the end of the right arm. Does not reliably balance mutations in the vicinity of ca. MacIntyre and Wright (FBrf0017571) observed about 9% double crossing over in the unbroken segment of the left arm from 61C to 74 on the polytene map and 15% recombination between the breakpoint at 96A and ca in In(3LR)TM2, Ubx¹³⁰ e/ru hry Diap1 st cu sr e^s Pri ca females that were also heterozygous for an X-chromosome inversion behaving like In(1)sc⁸ and In(2LR)SM1; no recombination observed in other regions. Some versions also carry p^p.