Wednesday, November 20, 2019

Mitosis Essay Example | Topics and Well Written Essays - 1000 words

Mitosis - Essay Example Cell division is a basic phenomenon of life in living organisms. It is known that the process of cell division, irrespective of the animal species, remains invariably the same. It is here that we comprehend that despite being the different in their outward appearance this basic phenomenon invariably remains the same. In byline, the author of the article, Daniel Needleman, has said that experimentation has been able to understand the difference that exists in this cell division phenomenon among the animals. This difference is found out to reside on the chromosomal and molecular level rather on higher level view. This difference can also exist even between similar organisms. Over a long period of time, it was known that spindle fibers that segregate chromosomes during cell division show great variation in size and shape, but the underlying reason was not discovered. Experiments have shown that the embryos that undergo the process of division, after repeated division cycles, considerabl y reduced in size and so did the spindle sizes. The experiments conducted on organisms like mouse have revealed many facts yet it has been difficult to ascertain any explicit cause to the phenomenon. Thus, another aspect that is attributed with the change is the change in biochemistry during the course of cell division. To infer a proximal result of the obvious phenomenon, a causative analysis is used as help. Cellular biology research has, therefore, evaluated a relationship during the course of development, between protein and phenotype. ... This experiment is multistage causal analysis procedure (Wilbur and Held). Embryos are subjected to tests during different stages of their development. It revealed that the change in size of spindles was not caused by division rather it was related to the state of cytoplasm. This in turn puts a question mark on how cytoplasm produces such change. To answer this question a categorization of the same microtubules was made. Early stages revealed less de-polymerization or catastrophe to these microtubules, as compared to those in the late stages. This revelation through stag-wise analysis did not reveal the true picture that could be able to answer above mentioned questions. Varying lengths of microtubules during the de-polymerization cannot be understandable reason. Later Wilbur and Heald used another approach to understand the size variation of spindles. Cytoplasm and its effects on elementary protein structures of spindles were analyzed. Proteins responsible for microtubule catastroph ies in different extracts were identified as Kinesin-13 and Kif2a. Kif2a was thought to be the reason of change in spindle sizes but extracts have revealed that concentration of this type of proteins remains constant during all stages of development. A co-existing phenomenon of importin-alpha attaching to the membrane or leaving the cytoplasmic area caused kif2a to be more active, that in turns increases microtubule catastrophy rates. (Wilbur Heald, 2013) Suggestion about this mechanism is perhaps understandable with the help of biochemistry, as with change in size due to successive divisions cause greater surface to volume ration than in larger cells. The only point in this understandable phenomenon is that why importin-alpha tends to be sequestered with the cell membrane

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