What is the role of telomerase in cells?

• A. It extends telomeres in germ cells and some stem cells
• B. It degrades telomeres
• C. It repairs double-strand breaks
• D. It synthesizes rRNA

Answer: (A)

Telomeres protect chromosome ends from being mistaken for DNA breaks, and they tend to shorten with each cell division due to the end-replication problem. Telomerase counteracts this by extending the ends of chromosomes: it’s a ribonucleoprotein that carries an RNA template and uses reverse transcription to add repetitive telomeric DNA to the 3' end. This activity is especially important in germ cells and many stem cells, which divide many times and thus rely on telomerase to maintain telomere length and genomic stability. In most somatic cells telomerase is not active, so telomeres shorten over time and cell division eventually halts. Telomerase does not degrade telomeres, does not repair double-strand breaks directly, and does not synthesize rRNA.