Drosophila melanogaster recombination experiments with inversion heterozygotes

Recombination suppression in chromosomal inversion heterozygotes is a well-known but poorly understood phenomenon. Surprisingly, recombination suppression extends far outside of inverted regions where there are no intrinsic barriers to normal chromosome pairing, synapsis, double-strand break formation, or recovery of crossover products. The interference hypothesis of recombination suppression proposes heterozygous inversion breakpoints possess chiasma-like properties such that recombination suppression extends from these breakpoints in a process analogous to crossover interference. This hypothesis is qualitatively consistent with chromosome-wide patterns of recombination suppression extending to both inverted and uninverted regions of the chromosome. The present study generated quantitative predictions for this hypothesis using a probabilistic model of crossover interference with gamma-distributed inter-event distances. These predictions were then tested with experimental genetic data (..., Stock Construction: Five inbred lines each carrying a different cosmopolitan paracentric inversion In(3R)K,In(3R)P, In(3R)C, In(3R)Mo, or the Standard arrangement (as an inversion-free negative control) were drawn from the Drosophila melanogaster Genetic Reference Panel (DGRP). Inversions and the inversion-fee negative control were identified by polytene chromosome squashes of third instar larva salivary glands and confirmed with PCR amplification of inversion breakpoints. Focal third chromosomes were isolated by balancer chromosome-assisted extraction and placed on a common, standard arrangement genetic background for the X, Y, mitochondrial, and second chromosomes (from DGRP line 399).
Three fully penetrant dominant phenotypic markers (Gl1, Sb1, and Dr1) were selected due to their position relative to inversion breakpoints. These markers were introgressed onto both the inverted arrangements and the standard arrangement (negative control) followed by repeated backcrossing for a minimum...,