THE GENERAL OUTLINE OF MEIOSIS 65 



The result of the first meiotic anaphase is often 

 said to be a separation of whole chromosomes instead 

 of the split halves of chromosomes as at mitosis. 

 While this is correct in a sense it must be pointed out 

 that the chromosomes which separate at the first 

 anaphase are not the same as the maternal and 

 paternal chromosomes which came together at 

 zygotene ; these have interchanged sections of their 



Fig. 16. — Diagrams showing the genetic consequences of the 

 first and second meiotic divisions. Maternal portions 

 black, paternal ones hatched. Three pairs of chromo- 

 somes are shown, each pair having possessed a single 

 chiasma. It will be seen that the first division is always 

 ' reductional ' between the spindle attachment and the 

 first chiasma, and the second division is always ' equa- 

 tional ' for this region. 



length by crossing over so that the actual chromo- 

 somes which separate at the first division are new 

 combinations of segments of the maternal and paternal 

 chromosomes (Fig. 16a). Between the spindle attach- 

 ment and the first point of crossing-over on either 

 side of it, however, the first anaphase always leads 

 to the separation of two maternal from two paternal 

 chromatids (Fig. 16j. 

 5 



