the division spindle. But, in many organisms it is formed in absence of
centrioles. Besides, it was established that if in animal cells the centrioles are
destroyed by laser rays, the division spindle continues its normal function.
That means that centrioles are not the structures assembling the microtubules
in a spindle. For that reason now the attention is directed to the two mitotic
centres, which under electron microscope look like shapely, weakly coloured
areas of amorphous material. It is possible replicated centrioles to have been
included additionally in the evolutionary process of animal cells by handing
down to the daughter cells in the course of division.
image
Figure 3–15. A scheme of meiosis and its comparison with usual mitosis. For clarity, only one pair of homologous chromosomes is shown (After Alberts et al., 1986).