Multiple Steps in the Molecular Causes of Cancer
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The cell is a beautiful machine that is very well protected from DNA mutation. A human consists of about 10 14 of these beautiful machines, each one of which is a copy of the single-cell, fertilized zygote formed at the moment of conception. Most of the 10 14 cells in the body are renewed continuously,raising the number of cell divisions in a human lifetime by more orders of magnitude. For example, approximately 250 billion neutrophils and an equal number of red blood cells are replaced every day of our lives by cell division. A very rough estimate is that, on the average, the cells in our body turn over once a month. At each one of these cell divisions,the 6 billion nucleotides of the human genome are faithfully copied. Again,a very rough estimate of the total number of nucleotides copied as DNA replicates during a 100-year lifetime is as follows:
(10 14 cellslhuman)(10 cell divisions for each cell/year)
(100 years/lifetime)(6 X 10 9 nucleotides/cell division)= approximately 10 27 nucleotides copied/human lifetime
KeywordsHuman Papilloma Virus Multiple Step Chemical Carcinogen Geiger Counter Neoplastic Clone
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