Elongation of DNA

The single-stranded protruding end of the telomere can be extended by telomerase, an enzyme with both a protein and an RNA component (also known as a ribonucleopro-tein). The RNA part of the enzyme contains from 15 to 22 nucleotides that are complementary to the sequence on the G-rich strand. This sequence pairs with the overhanging 3' end of the DNA (I Figure 12.20b) and provides a template for the synthesis of additional DNA copies of the repeats. DNA nucleotides are added to the 3' end of the

Conclusion: In the absence of special mechanisms, DNA replication would leave gaps due to the removal of primers at the ends of chromosomes.

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