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the cell cycle and mitosis - video notes station

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an adult human contains an estimated 100 trillion cells and yet we start Life as a single cell to grow develop and repair tissue we rely on cell division in eukaryotic cells this process is accomplished by a series of well-orchestrated steps called mitosis every day our bodies must produce millions of skin cells to replace those lost through normal activity each of these cells must have a complete end of the genetic material prior to cell division the cell divides into two identical cells the DNA needs to be replicated so that daughter cell receives an exact copy  following DNA replication the chromosomes condense in the nucleus of the cell DNA condenses by wrapping around Coors of histone proteins forming nucleosomes this beads on the string structure is called chromatin as a cell prepares to divide chromatin coils up further shortening and condensing the chromosome the replicated chromosomes hold sister chromatids  the replication of DNA and the formation of sister chromatids is one part of the entire cell cycle to prepare for cell division the cell goes through interphase which can be divided into three distinct phases during G1 or Gap one phase all the organelles and cytoplasmic components including the centrioles in animal cells replicate enduring s or synthesis phase the DNA replicates finally during G2 or Gap to phase all the enzymes need to Aid in the process of cell division are produced most eukaryotic cells spend a great deal of time in interphase and a very short period of time Charlie dividing a process called mitosis the cell is now ready to go through mitosis which consists of prophase metaphase anaphase and telophase during prophase the chromosomes condense and become visible appearing as two sister chromatids gather at the centromere the cytoskeleton disassembles as the spindle begins to form in animal cells cells play an important role in the distribution of the chromosomes in the dividing cell the centrioles migrate to opposite poles establishing a picture of microtubules called the spindle apparatus and the nuclear envelope breaks down towards the end of prophase chromosomes attach buy proteins in their centromeres called kinetochores to microtubules from each pole moving the chromosomes toward the equator of the cell during metaphase all chromosomes are aligned at the equator of the cell called the metaphase plate and a phase begins with the degradation proteins that holds sister chromatids together freeing individual chromosomes the free chromosomes are then pulled by their kinetochores to opposite Kohl's at telophase a cleavage Furrow forms in the center of the cell this indentation is made from a constricting belt of actin surrounding the inside of the cell circumference  chromosomes cluster at opposite poles and begin D condensing as the nuclear reforms around them the spindle apparatus disassembles as the microtubules are broken down into tubulin monomers that can be used to form the site skeleton of the daughter cells in animal cells cytokinesis complete cell division by extending the cleavage Furrow to complete separate the newly-formed daughter cells since plant cell walls cannot be constricted by actin fibers vesicles form and expanding membrane session called the cell plate like animal cells plant cells use cytokinesis to finish the division of the contents of the cytoplasm between the two identical car sales  during the cell cycle certain checkpoints are encounter to make sure the process is occurring accurately and if it is not cell cycle will stop at the checkpoint and correct or possibly inhibit that cell from dividing the first checkpoint is the G1 s checkpoint and is considered the primary point at which the cell cycle continues or stops external signals and growth factors can influence the cell cycle and affect the progress at or before this critical checkpoint the g2m checkpoint allows cells that have successfully completed all phases of interphase to begin mitosis the last checkpoint is the spindle checkpoint ensuring that all chromosomes have attached to the spin in preparation for anaphase growth factors the size of the cell and the nutritional state of the cell are all contributing factors in cell cycle regulation ensuring that only certain cells divide at appropriate times once all the checkpoints in interphase are cleared mitosis from interphase to cytokinesis the entire process of cell division can take on average 10 to 20 hours in a typical plant or an also depending on the nature and use of the cell the process can happen at different frequencies as well in humans are skin cells have a high turn for weight due to wear and tear and go through mitosis very frequently for as other cells such as adult neurons and muscle cells rarely divide the accuracy of mitosis as well as the consistency of the checkpoints during interphase ensure that most cells in a eukaryotic organism can produce identical of themselves this process allows for growth and repair to prolong overall physiology as well as life itself

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