Q32. Telomerase has a function similar to __________
(A) DNA dependent DNA polymerase
(B) RNA polymerase
(C) DNA gyrase
(D) Reverse transcriptase
Telomerase functions as a reverse transcriptase enzyme. This ribonucleoprotein complex uses its RNA component as a template to synthesize DNA repeats onto chromosome ends, maintaining telomere length during cell division.
Option Analysis
(A) DNA dependent DNA polymerase synthesizes DNA using a DNA template, as seen in replication enzymes like DNA polymerase III, but telomerase requires an RNA template instead. This makes the function dissimilar.
(B) RNA polymerase transcribes DNA into RNA, producing mRNA or other transcripts, whereas telomerase performs the opposite by making DNA from RNA. No similarity exists in directionality or product.
(C) DNA gyrase is a bacterial topoisomerase II that introduces negative supercoils into DNA to relieve torsional stress during replication, lacking any polymerase or reverse transcription activity. It plays no role in telomere maintenance.
(D) Reverse transcriptase is the correct match, as telomerase’s catalytic subunit (TERT) acts as an RNA-dependent DNA polymerase, adding TTAGGG repeats using its internal RNA template (TERC), just like retroviral reverse transcriptases.
Telomerase function similar to reverse transcriptase defines its unique role in eukaryotic cells. This enzyme prevents chromosome shortening by extending telomeres, crucial for CSIR NET Life Sciences exams.
Telomerase Mechanism
Telomerase reverse transcriptase (TERT) uses telomerase RNA (TERC) as a template to add TTAGGG repeats to 3′ chromosome ends, compensating for replication loss. Active in stem cells and cancer, it enables unlimited division unlike somatic cells.
Why Reverse Transcriptase?
Both enzymes synthesize DNA from RNA templates: retroviral versions integrate viral genomes, while telomerase maintains telomeres. TERT shares structural domains (fingers, palm, thumb) with viral reverse transcriptases.
Exam Relevance
In CSIR NET questions, telomerase’s RNA-dependent DNA polymerase activity distinguishes it from DNA-dependent options. Key for topics like DNA replication and aging.
