Peculiarities of Mitosis - Cleavage

From the following you will learn that the mitosis in the phase of cleavage has some striking peculiarities:

a) Synchronization of cell divisions of blastomeres: The early blastomeres divide simultaneously (synchronously) producing two blastomeres from zygote followed by 4,8,16,32 and so on, in most cases. However, such synchronization is lost, during later cleavage divisions.

b) No interphase between two successive divisions, i.e. here is no growth in the amount of cytoplasm in the derived blastomeres with the result that the size of daughter blastomeres continues to decrease during successive cleavages.

c) The size of the nucleus remains practically unchanged. Therefore the nucleus: cytoplasm ratio, which is very small in the fertilized egg cell or zygote, continues to increase in the blastomeres derived from successive cleavage divisions.

d) Rate of cell divisions is very rapid and very large number of cells is produced during cleavage. This is possible due to absence of interphase. The rate slows down later on.