Mitosis or cell division can be found in many areas of the body. Multicellular organisms can increase their size by replicating the number of cells using mitosis. Eukaryotes can reproduce asexually through mitosis to become two daughter cells. Tissue that has been damaged can be replaced by replicating the cells that are healthy. A fertilized egg (zygote) will go through mitosis to help its development into an embryo.
The life cycle of a cell can roughly be broken down into two parts; it's growth and divisionInterphase: growth of the cell, broken down into 3 specific stages; the G1, S, G2. G1 is the growth and maturation of the cell. S is where the DNA is replicated and G2 is when the cell prepares to divide. On occasion, there is even a G0 stage where the cell no longer divides
M Phase:
The M phase is the period of mitosis and cytokinesis. The nucleus, with the DNA within are split, and the the cytoplasm divides.
If cell division loses control, tumors can result at any of the organs or tissue. External or internal signals will excite the chemical control system that can influence the cell cycle. One such signal is produced by tumor suppressor genes that creates proteins that inhibit cell division. Mutations to these genes can lead to an explosion of cell divisions resulting in a tumor. Eventually, tumors can grow exponentially until it damages the surrounding tissue or spreads to other areas of the body. These tumors are known as cancerous
Interphase (G1, S, G2):
During the interphase stage of a cell, many active reactions will occur. Protein synthesis, DNA replication and the production of mitochondria and chloroplast all happen during this stage. These processes are done in preparation for division.
Protein synthesis: Significant proteins and enzymes are produced that help the cell grow, copy its organelles and DNA and essentially to prepare for cell division.
ATP Production: Lots of ATP will be used during cell division. This is also the reason for the increased number of mitochondria.
Organelles: Organelles will be copied so that the two daughter cells will have an exact replica of the organelles.
DNA replication: DNA must also be copied before division so that the daughter cell will possess the same genetic instruction.
All these processes occur during interphase which incorporates the G1, S and G2 phases.
G1: Stage before DNA replicates. The cell grows, organelles are replicated, proteins synthesized and ATP produced
S: DNA replication
G2: Copied DNA examined for mutations and more metabolic reactions occur.
Mitosis:
Prophase: DNA supercoils, chromosomes condense and are visible, two genetically identical sister chromatids (created in the S stage of interphase) are joined at a centromere. Centrosome move to opposite poles of the cell and spindle fibres are forming. Nuclear membrane is broken down and disappears
Metaphase: Centrosomes produce spindle fibres that attach the the centromere of each chromosome. Microtubule spindle fibres contract to force chromosomes to line up along equator of the cell
Anaphase: Further contraction of spindle fibers pull the chromosomes apart into their original two separate chromatids to each side. Now that the two chromatids are separate, they each constitute a chromosome.
Telephase: The chromosomes arrive at each pole, the spindle fibres dissolve and a new nuclear membrane forms around each set of chromosomes. Chromosomes decondense and the the cell divides into two daughter cells via cytokinesis
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