2. What are the phases of Mitotic division?
3. Explain the cell cycle control system?
1. Interphase: Interphase is the period in the cell cycle when the cell is not dividing. During interphase, cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size is may increase. Interphase accounts for $90 of the cell cycle. It has three parts. G1,S, and G2. In G1 part, cell grows. In S part, DNA is synthesized, and chromosomes are replicated. In G2 part, cell is prepared for division.
2. After Interphase, the phases are: Prophase, Prometaphase, Metaphase, Anaphase, Telophase and Cytokinesis.
Video on this mitotic cell division:
3. The cell cycle has interacting proteins that act as stop and go signals at specific points during the cycle. There are two major CHECKPOINTS. One is just before the cell enters the S phase, and the other is before entering Mitosis. If a cell is too small, or starved, or the environment cannot provide the proteins and energy necessary for the division, control proteins will delay the cell's attempt to duplicate itself. (Gzero) G1 checkpoint. p53 prevents cells with damaged DNA from proceeding to the S phase of the cell cycle. The cell can then attempt to repair the DNA and if succesful, go on to S phase. G2 checkpoint provides a safety gap before the cell plunges into Mitosis. The cell ensures that DNA replication is complete. The G2 checkpoint is similar to the G1 checkpoint in that it is a timing point at the end of g2 where STOP proteins can prevent mitosis until the cell has completed all the required steps for division.
5 main facts about the cell cycle:
. Prophase : In early prophase, the centrosomes move toward opposite poles of the cell, organizing the spindle microtubules between them. The sister chromatids become visible in the nucleus as they condense.
. The chromatids remain lined up between the poles of the cell during metaphase.
. Anaphase begins when the pairs of sister chromatids separate. The separated chromatids are now called chromosomes, and move towards the poles of the cell.
. The chromosomes arrive at the pole and the new nuclear membranes form around them in telophase.
. Division of the cytoplasmic components is called cytokinesis. The parent cell divides into two.
Cell cycle occurs in order to reproduce, grow, and repair the cell. The goal if the cell division is to split the sister chromatids and give one to each new cells. Regulation of cell division must be controlled by checkpoints. If the control system fails, the cancer cells occur. They do not stop dividing.
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