Conventional and unconventional analysis of an inversion inNeurospora

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Abstract
SUMMARY: In(IL; IR)O Y348is a pericentric inversion of linkage group I inN. crassa, with a breakpoint betweenfrandun-5in the left arm and a breakpoint betweenad-9andnit-1in the right arm. Approximate breakpoint location was found by tabulating crossovers between the rearrangement and markers in normal chromosome sequence. Inversion structure was verified by markedIn O Y348×In O Y348crosses. Precise mapping of breakpoints was by duplication coverage. Inversions likeO Y348do not produce progeny with segmental chromosome duplications when crossed to normal sequence, but duplications were produced by crossing it toIn(IL; IR)O Y323(Barry & Leslie, 1982), another standard pericentric inversion, and toT(I → VI)NM103(Turner, 1977), a translocation to a tip. Each of these rearrangements has a breakpoint within the inverted region ofIn O Y348. Two duplications fromIn O Y348×In O Y323were converted to normal chromosome sequence by double mitotic recombination. Besides expediting mapping, the technique of intercrossing rearrangements increasingly enables us to make segmental duplications exactly tailored for studying specific included genes.