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Unformatted text preview: polymerase cannot begin at the end of a strand. It can only add to an existing strand. The new DNA strand is shorter than the template strand. As a result of the inability of DNA polymerase to initiate synthesis, the DNA molecule becomes shorter with each cell division. Human chromosomes have the sequence "TTAGGG" repeated 100 to 1500 times at each end of the DNA strand. These repetitive sequences do not contain any genetic information. Each time a cell divides, 50 to 500 of these repeats are lost, making the DNA shorter. Short telomeres may prevent a cell from dividing. The length of telomeres, therefore, may limit the number of times a cell can divide. Telomerase is an enzyme that restores the length of telomeres. This enzyme is normally not found in somatic (body) cells but is found in germ cells....
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