Cytokinesis In Onion Lab Report

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Observation of mitosis in Onion root tips
Answer the following question to its full explanation:
1. What is Cytokinesis? Compare and contrast cytokinesis between plant and animal cells.
Cytokinesis is the last step in cell division, where the cytoplasm divide and the two daughter cells appear.
In Animals, the cytokinesis processes occurs through cleavage. Firstly, in the old metaphase plate position, a cleavage furrow is formed. On each sides of the furrow, a contractile ring formed of actin microfilaments. These actin microfilaments interact with myosin protein, which causes the contraction of the ring. This contraction is acting on pulling the rings so the furrow goes deeply until separating the cell into two cells. In plants, cytokinesis
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5. What is the role of the centrosome (the area surrounding the centrioles)? Is it necessary for mitosis? Defend your answer.
Centrosome is the regions that responsible for formation of spindle fibers from the microtubules. These spindle fibers are needed for pulling the chromosomes apart from each others in anaphase. It is necessary for formation of the microtubules and without the centrosome, there will not be any separation of the chromosomes and genetic disorders will develop.
6. What are advantages of using onion roots for viewing mitosis?
The onion roots are useful in showing the mitosis stages because they have fast division rate. Additionally, their chromosomes are stained darker and look bigger.
7. Estimate the percentage of time the onion root tip cells spend in each different stage of the cell cycle in the table below. Calculate the mitotic index and explain you result. Number of cells Percent of total cell counted Timing
(assuming that the cell spend 24 hrs) Field 1 felid 2 Felid 3 Total
Interphase 30 30 11 71 75% 0.75*24=18 hrs
Prophase 5 3 4 12 12.5% 0.125*24=3

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