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Some of the main types of mitotic abnormalities are as follows:
Various mitotic abnormalities are formed as a result of placing the cells in unfavourable conditions during different phases.
Physical agents, such as temperature, radiations and chemicals like narcotics and enzyme inhibitors, can easily produce mitotic deformities.
1. Cytasteral mitosis:
Wilson (1901) noticed formation of numerous asters in cytoplasm of unfertilized eggs called cytasters by placing them in hypertonic sea water.
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In the eggs of marine invertebrates, production of many small cytoplasmic asters is of frequent occurrence. Intermixing of nucleoplasm and hyaloplasm seems to be necessary condition for aster formation.
Costello (1940) showed that asters can be produced only if germinal vesicle has broken down.
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2. Multipolar and caternar mitosis:
Mitotic divisions showing several spindles and Centrosome are common in many Protozoa and fish eggs. Multipolarity is usually caused by uneven division of Centrosome as well as irregular distribution of chromatids on different spindles. It results in the formation of cells as aneuploidy (uneven chromosome number).
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Caternar mitoses have been described by Dalcq and Simon (1932) in amphibian eggs. During this, dividing cell forms a large number of asters without spindles or chromosomes to link them. It suggests that asters are capable of dividing in the absence of spindle or nucleus in an autonomous way.
3. Achrosomal mitosis:
Sometimes, mitosis is induced by various agents without use of nucleus or chromosomes. Briggs et al., (1951), in fertilized eggs with heavily x-rayed sperms, removed the egg’s maturation spindle by pricking and sucking. In this way, he obtained very nice non-nucleate blastulae. Similarly, Stauffer (1945) obtained normal non-nucleated Axolotl blastula.
4. Anastral mitosis:
In plant cells and many oocytes, generally asters around the Centrosome are absent, thus producing Anastral mitosis. Bataillon and Tchou Su (1933) described in details the Anastral mitosis in amphibian inter—specific hybrids.
5. С-Mitosis (abnormal spindle formation):
Brachet (1957) has described that colchicine inhibits mitosis by disorganizing spindle formation. The results are the formation of polyploid cells, and reduplication of chromosomes. Besides, during mitosis, sometimes cell nucleus is either deformed into a single spheroid compact mass (pycnosis) or becomes broken down (karyorrhexis).
