Which enzyme extends telomeres by using an RNA template to add repeats in eukaryotic cells?

Which enzyme extends telomeres by using an RNA template to add repeats in eukaryotic cells?

• A. Helicase
• B. DNA polymerase
• C. Telomerase
• D. Ligase

Answer: (C)

Extending chromosome ends requires a specialized enzyme that can add DNA repeats using its own RNA as a template. Telomerase carries an RNA component that serves as the template for synthesizing telomeric repeats directly onto the 3' end of chromosomes. It functions as a reverse transcriptase, turning that RNA template into DNA repeats (such as TTAGGG in humans). This unique activity sets it apart from other enzymes: helicase only unwinds DNA, DNA polymerase copies DNA using a DNA template, and ligase seals nicks after synthesis. After telomerase adds the repeats, the rest of the replication machinery can finish the process, but the direct extension of telomeres with an RNA template is the defining role of telomerase.

Extending chromosome ends requires a specialized enzyme that can add DNA repeats using its own RNA as a template. Telomerase carries an RNA component that serves as the template for synthesizing telomeric repeats directly onto the 3' end of chromosomes. It functions as a reverse transcriptase, turning that RNA template into DNA repeats (such as TTAGGG in humans). This unique activity sets it apart from other enzymes: helicase only unwinds DNA, DNA polymerase copies DNA using a DNA template, and ligase seals nicks after synthesis. After telomerase adds the repeats, the rest of the replication machinery can finish the process, but the direct extension of telomeres with an RNA template is the defining role of telomerase.