Answer: It adds telomeric repeats to chromosome ends, preventing shortening.
- A It repairs double-strand breaks scattered throughout the chromosome arms
- B It adds telomeric repeats to chromosome ends, preventing shortening
- C It deposits methyl marks onto histone tails to silence chromosomal regions
- D It excises the RNA primers left behind after lagging-strand synthesis
Correct answer: B. It adds telomeric repeats to chromosome ends, preventing shortening
Explanation: Telomerase is a reverse transcriptase that extends telomeres. Normal somatic cells lack telomerase, so chromosomes shorten with each division (Hayflick limit). Cancer cells and stem cells reactivate telomerase.
As substrate concentration rises, reaction rate increases steeply at first, then plateaus at Vmax once every enzyme molecule is working at full capacity; Km is the substrate concentration giving half-maximal rate, and a LOWER Km means the enzyme reaches that rate with less substrate (higher affinity).
Concept context
Carbohydrates, proteins, lipids, nucleic acids, and enzyme kinetics. Essential foundation for understanding metabolism.