Chiasma interference is blind to centromeres.

It has long been assumed, since the early works of Mather, that the centromere plays a central role in chiasma position determination, so much so that in all sequential models chiasma determination was supposed to start or finish at this point. More specifically, it has been assumed that the centromere acts as a barrier to the transmission of interference, so that a chiasma in the vicinity of a centromere would not affect the probability of chiasma formation across at this point. Some statistical analyses seemed to ratify this supposition. However, a reassessment of the literature led us to the conclusion that the statistical analyses that were not flawed were consistent in showing that interference may act across the centromere. Using large sets of chiasma data from the grasshoppers Leptysma argentina and Chorthippus brunneus and applying statistical approaches that involved either the calculation of coincidence or correlating the distances between the centromere and the nearest chiasma in either arm, it is concluded: 1. that interference acts across the centromere; 2. that the action of interference is not changed by the presence of an intervening centromere.