A POLYMORPHIC CENTRIC FUSION ENHANCES CHIASMA INTERFERENCE IN LEPTYSMA-ARGENTINA (ORTHOPTERA) - A CHIASMA DISTRIBUTION STUDY

A chiasma distribution study in diplotene in the grasshopper Leptysma argentina revealed that: (i) chiasma interference plays a central role in determining chiasma distribution in bivalents carrying two or more chiasmata in this species; (ii) the distance of interference (i) increases significantly in fusion carriers, and this effect is additive (is more pronounced in fusion homozygotes than in heterozygotes). This increase is due to a genuine intensification of chiasma interference; (iii) chiasma interference is operative across the centromere; and (iv) across-centromere interference is also influenced by the karyotype, in the same fashion as non trans-centromeric interference. Finally, a discussion concerning the possible origin of the fusion 3/6 polymorphism is held.