Defects in nuclear transport enhance segregation distortion

The equal segregation of chromosomes into gametes is a central tenet of Mendelian genetics. It is this process that is responsible for generating predictable outcomes of crosses, as well as subjecting all chromosomes to the natural selective pressures that exert themselves on a population. Meiotic drive systems violate the principle, and result in a distortion of normal Mendelian ratios. Examples of such meiotic drive systems exist in many organisms, including insects, mammals and plants (reviewed in Lyttle).1 The most clearly understood of these is the Segregation Distorter (SD) system in Drosophila melanogaster. SD was first observed because males carrying one SD chromosome and one normal (SD+) chromosome failed to transmit the normal chromosome to their offspring, causing transmission ratios of near 100% of the SD chromosome.2 T