Biology Questions

Biology Questions

Processes of Cytokinesis in Animal and Plant Cells

The first step in cytokinesis in animal cells is the contractile ring positioning. The difference between cytokinesis in plants and animals arises from this stage itself. Animal cell cytokinesis begins just after the onset of sister chromatid separation in the anaphase of mitosis.

As mentioned earlier, cytokinesis in plants and animals is basically different from each other due to the presence of cell wall, which is one of the plant cells parts. Rather than forming a contractile ring, plant cells form a cell plate in the middle of the cell (Eggert, 2006). The Golgi apparatus releases vesicles that contain cell wall materials. These vesicles fuse at the equatorial plane to form the cell plate. The cell plate initially begins as a fusion tube network, which then becomes a tubulo-vesicular network as more and more components are added.

Role of Cell Division

In reproduction-without cell division mitosis could not be effected, as a result no reproduction could be effected, thus no new generations. So, cell division in living organism is used for reproduction process.

In growth-cell divisions allows growing of an organism, since increase in cell number allows differentiation of body structures of an organism.

Repair of injured parts-cell division aid to increase number of cells which aid to repair an injured area of an organism.

Cell or Tissue Engage in Mitosis

Mitosis is the process in which one eukaryotic cell divides into two cells identical to the parent cell (generally identical, since alterations in genetic material can occur, more or less organelles may be distributed between the daughter cells, etc.)

Mitosis is fundamental for asexual reproduction of eukaryotes, for the embryonic development, for the growth of pluricellular beings and for tissue renewal (Raven, 2005).

Generally in vertebrates mitosis is more frequent in tissues that require intense renewing due to their functions, like epithelial tissues and the bone marrow. In plants the meristem tissue has numerous cells undergoing mitosis.

Chromosome and Chromatid

Though these terms are closely related and very confusing to each other, there are still a lot of things that differs each one of them. A long and continuous strand of DNA is what Chromosomes are but when two chromatids are united together with a centromere, it produces one chromosome. Chromosomes, as mentioned above, are vectors of heredity or the ones that carries the genes of one organism to the other like the physical appearance and different characteristics while Chromatids are the ones who made possible the replication of these cells (Maton, 1997).

Changes during Metaphase

In metaphase, the spindle fully develops and the chromosomes align at the metaphase plate.

Changes that occur in a cell during metaphase (Morgan, 2007): 

The nuclear membrane disappears completely.

In animal cells, the two pair of centrioles align at opposite poles of the cell.

Polar fibers (microtubules that make up the spindle fibers) continue to extend from the poles to the center of the cell.

Chromosomes move randomly until they attach (at their kinetochores) to polar fibers from both sides of their centromeres.

Chromosomes align at the metaphase plate at right angles to ...