114 



AN INTRODUCTION TO MODERN GENETICS 



the simpler cases the fact that the chromosomes were separate at their 

 first appearance could be conclusively demonstrated. The only other 



PROPHASE 



LEPTOTENE 



ZYCOTENE 



DIPLOTENE 

 OlAKINESIS (/) 



CO 



LT) 



METAPHASE 



~^^;:-v 



:: ^-^ 



ANAPHASE 



.4f^^»>^ 



TELOPHASE 



Fig. 54. The Relation of Mitosis and Meiosis (according to Darlington).— The 

 stages of mitosis are shown on the left, and the corresponding stages of meiosis 

 on the right. Note that the chromosomes are double at their first appearance in 

 mitosis, but not in the earliest (leptotene) stage of meiotic prophase. They pair 

 in zygotene, beginning to become double (split) in pachytene, and are double in 

 the last stages of meiotic prophase (diplotene and diakinesis). In mitosis anaphase 

 begins by the division of the centromeres, but in meiosis this does not occur 

 till the anaphase of the second division (not shown). 



