How do telomeres solve the problem of shortening DNA?
Though they can be copied in the normal fashion during DNA replication, they can also be extended by an independent mechanism catalyzed by the enzyme telomerase, which has both RNA and protein. Telomerase RNA has the reverse complement of the human telomere repeat and so can base-pair to the single strand DNA overhang, allowing extension, translocation of telomerase, and then extension again. Telomerase only adds to the end of the G-rich strand. However, C-rich strand elongation occurs when the G-rich strand is long enough. The primase-DNA polymerase alpha complex ataaches to the end of the C-rich strand and initiates synthesis of a new Okazaki fragment. It will still be shorter than the G-rich strand, bt the overall length of chromosomal DNA has not been reduced.