Which statement about telomerase components and its RNA template role best describes telomerase?

• A. A protein complex that degrades telomeres.
• B. Telomerase comprises a protein reverse transcriptase (TERT) and an RNA component (TERC) that provides the template to extend telomeres.
• C. A ribosome-like particle that translates telomeres.
• D. A DNA polymerase that extends telomeres using a DNA template.

Answer: (B)

Telomerase is a ribonucleoprotein enzyme that extends chromosome ends by using its own RNA as a template and a protein component with reverse transcriptase activity. The RNA component provides the template sequence that is copied into DNA to add telomeric repeats to the 3′ end of the chromosome. In humans, this template guides the addition of the TTAGGG repeat sequence, enabling telomere elongation with each replication cycle. The protein component, TERT, does the reverse transcription—from RNA to DNA—making telomerase different from ordinary DNA polymerases that use a DNA template. This combination—a reverse transcriptase enzyme plus an RNA template—precisely matches the description in the statement. The other ideas describe proteins that degrade telomeres, ribosome-like particles that translate sequences, or DNA polymerases acting on a DNA template, none of which capture the essential RNA-templated reverse transcription mechanism of telomerase.