Practice question

End replication problem arises because DNA polymerases require primer and synthesize only 5' to 3', leaving lagging strand telomere unable to be fully replicated after removal of terminal RNA primer. Telomerase overcomes this by specialized ribonucleoprotein containing intrinsic RNA template complementary to telomeric repeat and protein reverse transcriptase subunit TERT that extends 3' G-rich overhang adding TTAGGG repeats in humans. Extension creates substrate for primase-pol alpha fill-in of complementary C-rich strand, maintaining telomere length, preventing senescence, and supporting immortalization of germline and cancer cells.