45. The Telomerase enzyme is a:
(a) DNA–dependent DNA Polymerase ,
(b) DNA–dependent RNA Polymerase ,
(c) Reverse Transcriptase ,
(d) RNA–dependent RNA Polymerase

 

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Telomerase Enzyme: A Unique Reverse Transcriptase in Chromosome Stability

Telomerase is a specialized enzyme crucial for the maintenance of chromosome ends, known as telomeres. These telomeres protect DNA from degradation and prevent the loss of genetic information during cell division.

But what kind of enzyme is telomerase, and how does it work?

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The Function of Telomerase

Each time a cell divides, telomeres shorten, eventually leading to cellular aging or senescence. Telomerase counteracts this by extending the telomeric DNA, ensuring genomic integrity is preserved over multiple divisions, especially in germ cells, stem cells, and cancer cells.

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Why Telomerase is a Reverse Transcriptase

Telomerase is classified as a reverse transcriptase because:

• It uses an RNA template that is part of its own structure (called TERC – Telomerase RNA Component).

• It synthesizes DNA from this RNA template.

• This is the defining feature of reverse transcriptases.

Hence, the correct classification of telomerase is:

(c) Reverse Transcriptase

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Evaluating Other Options

• (a) DNA–dependent DNA Polymerase
  These enzymes replicate DNA using a DNA template — telomerase does not do this.

• (b) DNA–dependent RNA Polymerase

• These enzymes transcribe RNA from DNA templates — not the function of telomerase.

• (d) RNA–dependent RNA Polymerase
   These are found in some viruses that replicate RNA genomes — not applicable to telomerase.

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Conclusion

Telomerase is a reverse transcriptase because it synthesizes DNA using its own RNA template. This function is essential in preserving telomere length and plays a significant role in cellular longevity and certain diseases, including cancer.