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The study of the cell cycle focuses on mechanisms that regulate the timing and frequency of DNA duplication and cell division. As a biological concept, the cell cycle is defined as the period between successive divisions of a cell. During this period, the contents of the cell must be accurately replicated. Microscopists had known about cell division for more than one hundred years, but not until the 1950s, through the pioneering work of Alma Howard and Stephen Pelc, did they become aware that DNA replication took place only at a specific phase of the cell cycle and that this phase was clearly separated from mitosis. Howard and Pelc's work in the broad bean, Vicia faba, revealed that the cell goes through many discrete phases before and after cell division. From this understanding, scientists then identified the four characteristic phases of the cell cycle: mitosis (M), gap 1 (G1), DNA synthesis (S), and gap 2 (G2). The study of these phases, the proteins that regulate them, and the complex biochemical interactions that stop or start DNA replication and cell division (cytokinesis) are the primary concerns of cell cycle biologists.
The most significant progress in this research field came with the demonstration that specific protein complexes involving cyclins were critical for regulating the passage of cells through the cell cycle. These early observations came from biological studies of the cells of rapidly dividing fertilized frog eggs as well as mutant yeast cells that could not divide. The observations suggested that regulation of the cell cycle is conserved throughout eukaryotes, which has since proved to be the case. The mechanism of division in bacteria differs from that of eukaryotes, and the control of their cell cycle is also somewhat different, although again it is linked with DNA replication.
Although the cell cycle is a highly integrated process, distinct areas of interest within this field of study have emerged. For instance, many genes and proteins that influence the passage from one phase of the cell cycle to another have been identified. When their expression is altered by mutation or aberrant regulation, they are usually classed as oncogenes. Other proteins act to hold the cell at distinct points in the cycle (checkpoints) and are known as tumor suppressor genes. Apart from those with a clearly regulatory role, many proteins have important functions in other aspects of the cell cycle; one is replication of DNA and organelles, which is a fascinating process that includes its own repair mechanisms and self-editing. Other fields focus primarily on the mechanical processes of cell cleavage into two daughter cells at the end of mitosis and on the condensation and decondensation of chromatin.
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Sometimes we underestimate ourselves, but in reality, sometimes we are the most essential thing. We are the difference of a million infinities, and completely going into oblivion.
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Line 61-81. The opposing view that king addresses in his counterargument is about how America will never change and be truly free from slavery until the people before us let it go as well.
Between lines 82–87 the effect of Martin Luther King mentioning his Nobel Prize is to explain why he is against the Vietnam war after people started questioning his opinion on the ending of the Vietnam wa
Answer: The answer is B
Explanation: I asked siri for the definition lol. By the way, if you had your phone, why didn’t you just look up the definition?
