Telomerase is an enzyme that is produced only in cells that are actively dividing. Thus, as a rule, it is...
GMAT Critical Reasoning : (CR) Questions
Telomerase is an enzyme that is produced only in cells that are actively dividing. Thus, as a rule, it is not present in adult tissue. Bone marrow is an exception to this rule, however, since even in adults bone marrow cells continually divide to replace old blood cells. Cancers are another exception, because their cells are rapidly dividing.
The information provided most strongly supports which of the following?
Passage Visualization
| Passage Statement | Visualization and Linkage |
|---|---|
| Telomerase is an enzyme that is produced only in cells that are actively dividing. | Establishes: Exclusive production rule Pattern: Dividing cells → Telomerase present Example: 1,000 actively dividing cells = 1,000 cells with telomerase Counter-example: 1,000 non-dividing cells = 0 cells with telomerase |
| Thus, as a rule, it is not present in adult tissue. | Establishes: General adult tissue rule Implication: Most adult cells are not actively dividing Example: Adult heart muscle - 10,000 cells examined, 0 with telomerase Example: Adult brain tissue - 5,000 cells examined, 0 with telomerase |
| Bone marrow is an exception to this rule, however, since even in adults bone marrow cells continually divide to replace old blood cells. | Establishes: Exception #1 with causal explanation Logic chain: Blood replacement need → Continual division → Telomerase present Example: Adult bone marrow - 1,000 cells examined, 800+ with telomerase • Validates initial rule: dividing cells have telomerase |
| Cancers are another exception, because their cells are rapidly dividing. | Establishes: Exception #2 with causal explanation Logic chain: Rapid cellular division → Telomerase present Example: Cancer tissue - 1,000 cells examined, 900+ with telomerase • Further validates: dividing cells consistently have telomerase |
| Overall Implication | Key Pattern Revealed: Telomerase serves as a reliable biomarker for cellular division activity. The "exceptions" actually prove the rule - they occur precisely where cells must divide, confirming the enzyme-division relationship is absolute. |
Valid Inferences
Inference: Cancer cells can be expected to contain telomerase.
Supporting Logic: Since telomerase is produced only in actively dividing cells, and cancer cells are rapidly dividing, cancer cells must contain telomerase. The passage establishes this as an absolute relationship with no stated exceptions to the enzyme-division rule.
Clarification Note: This inference is supported by the passage's logical structure, but the passage doesn't specify whether all cancer types or all cancer cells within a tumor would contain telomerase.