Modification of mitosis, Biology

MODIFICATION OF MITOSIS

1.      CRYPTOMITOSIS OR PROMITOSIS :

Primitive type of mitosis. In this mitosis nuclear membrane not disappear (remain intact throughout the division). All the change of karyo kinesis occur inside nucleus even the formation of spindle (intranuclear spindle) centriole is absent. Occur in some protozoa animal during binary fission eg. amoeba.

2.      DINOMITOSIS :

Cell division of dinoflagellate. Dinoflagellate are mesokaryotyes Eukaroytes in which chromatid threads without histone due to absence of histone, chromosome fail to condense properly so chromosome are not distinclly visible during division.

3.      FREE MUDELUR DIVISION :

Karyo kinesis is not followed by cytokinesis. These lead to coenocytic condition. eg. acellular slime mouldes, endosperm.

4.      ENDOMITOSIS :

Division or duplication of chromosome without division of nucleus. Endomitosis lead to polyploidy. Increase no of set chromosome. Colchicine induce polyploidy in plants. It is a mitotic poison. Interferes in normal mitosis retards the arrangement of spindle fibre. Arrest the cell cycle at metaphase.

Besides colchicine Mustard gas and Ribonucleases are also mitotic poison. They inhibit protein synthesis. Stop cell cycle in G phase. Total blockage of mitosis occur.

Posted Date: 10/8/2012 3:29:22 AM | Location : United States







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