Introductory Biology

6.2 The Cell Cycle

The cell cycle is a process which keep diving cells. The cells go through 4 phases during the cell cycle: G1, S, G2, and mitosis. The cell cycle starts off with a newly formed cell (G1). This is the first growth phase where the chromosome only has one chromatid and one centrometer. Only the healthy cells can go to the next phase,  syntheis phase, where the DNA is copied and chromosome of 2 chromatids are produced, as well. The cell moves on to the second growth phase (G2) which prepares the cell for mitosis/ construct the microtuble. Two identical nuclei are produced in the mitosis phase when the nucleus divides and the chromatids of each chromosome are separated. *Cytokinesis is when the cytoplasm divides and make two daughter cells.

G1, S and G2 are called the interphase and each process has a checkpoint to keep cells from having too much division. The first checkpoint is the cell growth G1) checkpoint: makes sure if the cell is big enough and the environment is suitable. The next checkpoint, Dna synthesis (G2) checkpoint, is when the DNA is checked by the DNA repair enzymes and the cell is in good environment with no mistakes in copying. The mitosis checkpoint is the final checkpoint the cell goes through where the chromosomes are checked if they are aligned properly and the end of the mitosis produces a transition cytokinesis, then the cell goes back to G1. Approximately 300 million new cells are produced per minute in our body. They are mostly produced when we are asleep because we are not using energy.

A normal cell (oncogenes) changes to a cancer cell if the brake is broken and the normal cell goes through the cell cycle too fast. The cancerous cell is a cell where the mutant changed a gene that can lead to cancer. Unlike normal cells, cancer cells go out of control in the cell cycle and the do not stop dividing. They are dedicated to make copies of itself (mutated) and keep dividing over and over again. Malignant tumor is when the cancer cells spread through whole the whole body. The worst case of the cancer cell is when the cells spread all over your body and to other tissues and can cause death, malignant cancers. Not only humans but trees can have a tumor as well. Proto-oncogenes act normal cell division though mutation can change proto-oncogenes to oncogenes, which overstimulates cell division. Tumor suppressor genes prevent uncontrolled cell growth though they fail to suppress cell division when mutated. The pro-oncogenes and tumor help balance the rate of cell division. Normal cells know when to stop and the proteins are made. Uncontrolled cell division produce either tumor or cancer when enough mutations accumulate. Cancer occurs when mutated genes overstimulate cell division (uncontrolled mitosis) and produce a tumor, a mass of cells.



One thought on “6.2 The Cell Cycle

  1. Yurika,

    Excellent entry for 6.2 on the cell cycle. You’ve covered the ideas thoroughly and with depth.

    Mr. F.

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