Posted by Sarah on Monday, July 31, 2006 at 8:30pm.
I can't figure out the correct answer for this, please help.
The drosophila embryo goes through a series of mitotic divisions before cytokinesis occurs. This demostrates one of the following.
1: cytokinesis is inextricably associated with mitosis
2. mitosis is always followed by cytokinesis
3: cytokinesis is never associated with mitosis
4: cytokinesis is inextricably associated with mitosis
Why are 1 & 4 the same?
2. is very often true, but not always.
So I guess 1 & 4
Cytokinesis is the division of the cytoplasm in a cell, which usually occurs immediately after nuclear division in mitosis. Cytokinesis is necessary to ensure a constant chromosome number in each cell. In mitosis, the chromosome number doubles, resulting in there being two sets of chromosomes in just one cell. The process of cytokinesis then results in two cells, each with their own single set of chromosomes. In animal cells, a process known as cleavage is undergone, in which the cytoplasm constricts at the centre. A ring of microfilaments (structural proteins polymerized in a helical form) forms in the middle of the cell, and as they constrict, the cell begins to pinch into two parts. As these parts separate, the cell surface shows very active movement, called “bubbling”. In plant cells, a dividing plate known as the cell plate forms across the centre, separating the two daughter cells, then forms a new cell wall. One notable exception to the normal process of cytokinesis is oogenesis (the creation of an ovum in the ovarian follicle of the ovary), where the ovum takes almost all the cytoplasm and organelles, leaving very little for the resulting polar bodies, which then die.
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