1.6 - B - Mitosis
Mitosis is the division of the nucleus into two genetically identical daughter nuclei. This process allows the cell to divide into two new daughter cells, each having the same genetic material as the parent.
The process of mitosis consists of four primary phases and occurs after chromosomes have been replicated. Chromosomes entering mitosis consist of two sister chromatids connected at a structure called the centromere.
Cytokinesis is the process in which the cell physically divides its membrane and cytoplasm in two. It results in two distinct cells with genetically identical nuclei and occurs differently in animal and plant cells:
In animal cells, the plasma membrane is pulled inward around the equator to form a cleavage furrow. Thi sis done using a ring of contractile proteins inside the membrane. When the cleavage furrow reaches the center, the cell is pinched apart into two daughter cells.
In plant cells, vesicles move to the center of the cell where they fuse to form a tube structure. When this tube is long enough, it forms the membrane of the two daughter cells. Then, pectins and other substances are released between the two new membranes (via exocytosis). Then, the daughter cells bring in cellulose and build new cell walls.
When observing the micrograph of a sample, you can determine the state of a cell by looking at the structure and distribution of its chromosomes. The photo on the left shows plant cells at various stages of mitosis.
Use the equation above to determine the mitotic index of the following micrograph