Chapter 9 Section 2: Mitosis and Cytokinesis Ms. Diana and Ms. Su’ad

Mitosis During Mitosis, the cell’s replicated genetic material separates and the cell prepares to split into two cells. The key function of mitosis is to accurately separate the cell’s replicated DNA in order to create two daughter cells that are genetically identical. Organisms use mitosis as a way of reproducing more cells and as a way to replace damaged cells.

Prophase Prophase – the first and longest phase. Mitosis is divided into 4 stages: Prophase – the first and longest phase. Nuclear membrane breaks down Nucleolus disappears Chromosomes condense Spindle apparatus (help move and organize the chromosomes before cell division) begins to form between the poles

Prophase In prophase, the chromosomes have the shape of an X. Each half of the X is called a sister chromatid. Sister chromatids – structures that contain identical copies of DNA. The structure in the center of the chromatid, the centromere is important because it makes sure a complete copy of the replicated DNA will become part of the daughter cell.

Metaphase Metaphase – the second and shortest stage of mitosis. The chromatids are pulled by motor proteins along the spindle apparatus toward the center of the cell and they line up in the middle. It ensures that the new cells have accurate copies of the chromosomes.

Anaphase Anaphase – 3rd stage of mitosis where the chromatids are pulled apart. The microtubules of the spindles begin to shorten and pull at the centromere of each sister chromatid. This causes the sister chromatids to separate into two identical chromosomes. At the end of anaphase, the microtubules move the chromosomes toward the poles of the cell.

Telophase Telophase – final stage of mitosis. The chromosomes arrive at the poles of the cell and begin to relax, or decondense. Two new nuclear membranes begin to form and the nucleoli reappear. The spindle apparatus falls apart and the left over microtubules are recycled by the cell to build parts of the cytoskeleton.

Cytokinesis Towards the end of mitosis, the cell begins the process of cytokinesis. Cytokinesis – division of the cytoplasm by using microfilaments to ‘pinch’ the cytoplasm. The result is two cells with identical nuclei. In plant cells, instead of pinching in half, a new structure called a cell plate forms between the two daughter nuclei.

Mitosis : A closer look

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