Telomerase transcription in proliferative cells

Steps:

• Identify cells needing indefinite division: stem, germ, and cancer cells maintain telomeres via telomerase.
• Recall telomerase role: adds telomeric repeats to chromosome ends, countering replication shortening.
• Match to options: assume 1=stem cells, 2=germ cells, 3=cancer cells, all transcribe telomerase.
• Confirm: somatic cells repress it, but these three express it for longevity.

Why A is correct:

• All three cell types (stem, germ, cancer) actively transcribe telomerase to enable unlimited mitotic divisions without telomere loss, per telomere maintenance biology.

Why the others are wrong:

• B: Excludes cancer cells, which highly express telomerase for immortalization.
• C: Excludes germ cells, essential for transmitting full telomeres to offspring.
• D: Excludes stem cells, required for tissue renewal without senescence.

Final answer: A