Telomerase transcription in proliferative cells

Steps:

• Telomerase adds telomeres to chromosome ends, preventing shortening during replication.
• It's transcribed in cells requiring indefinite division to maintain telomere length.
• Germ cells (1) express it for gamete longevity.
• Stem cells (2) use it for self-renewal.
• Cancer cells (3) reactivate it for uncontrolled proliferation.

Why A is correct:

• Telomerase is actively transcribed in all three cell types (germ, stem, cancer) to support high replicative potential, per telomere biology.

Why the others are wrong:

• B excludes cancer cells, which highly express telomerase for immortality.
• C excludes germ cells, essential for telomere maintenance in reproduction.
• D excludes stem cells, needed for tissue regeneration.

Final answer: A