Question

Explain the function of the telomerase enzyme in eukaryotic DNA replication.

Answer 1

Ans:

All eukaryotic chromosomes have repitative nucleotide sequences end, called telomeres that protect chromosome from deterioration or from fusion of neighbouring chromosomes. The normal replication generates multiple copies of telomeric repeats but fails to replicate the extreme 5' end of each chromosome strand. Telomerase is the special enzyme that replicate the telomeric ends.

Telomerase is a large ribonucleo-protein and function as reverse transcriptase that synthesize DNA using RNA as template. The enzyme recognizes the G-rich tip strand of existing telomere DNA repeat sequence and elongate it in the 5'-to -3' directions. The Telomerase synthesizes new copy of the repeats using an RNA template that is a component of the enzyme itself. After several rounds of extensions of parental strands by the telomerase, the lagging strand replication at the chromosome end can be completed by using these extensions as a template for complementary strand synthesis by DNA polymerase. This C-A rich complementary strand is possibly synthesized by using 3'-OH of the terminal G-T in the hairpin as a primer for DNA synthesis.

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