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Cancer - Principles & Practice of Oncology
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1999-06-07
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FIGURE 6-6. The end replication problem and role of telomerase in
circumventing it. The end of a DNA molecule is replicated on one
strand by continuous replication proceeding to the end of the
molecule, while the other strand is replicated discontinuously
utilizing RNA primers and Okazaki fragments. Removal of the RNA
primers and Okazaki fragment ligation leaves a region at one end of
each daughter molecule unreplicated. If there were no mechanism to
fill the gap, the chromosome end would get shorter with each round of
replication. Telomerase solves this problem by extending the 3' end of
the parental strand, thus providing an elongated template for the DNA
polyermase to utilize. This allows the entire original genomic DNA
sequence to be completely replicated. (After Greider CW. Bioessays
1990;12:363)