I have tested two contending views of chromosome-to-pole movement in anaphase. Chromosomes might be pulled poleward by a traction fiber consisting of the kinetochore microtubules and associated motors, or they might propel themselves by a motor in the kinetochore. I cut through the spindle of demembranated grasshopper spermatocytes between the chromosomes and one pole and swept the polar region...

One of the stronger empirical generalizations to emerge from the study of genetic systems is that achiasmate meiosis, which has evolved 25-30 times, is always restricted to the heterogametic sex in dioecious species. usually the male. Here we collate data on quantitative sex differences in chiasma frequency from 54 species (4 hermaphroditic flatworms, 18 dioecious insects and vertebrates and 32...