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About This Drill
AP Biology — Unit 4 — Cell Cycle & Regulation — Drill 15 is a practice drill. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.
Analyze cell cycle phase distributions in normal and tumor cell lines, and evaluate how CDK inhibitors and checkpoint proteins regulate cell division.
Passage
Researchers studying cancer biology examine cell division in two human cell lines: a normal epithelial cell line (Line N) and a tumor-derived cell line (Line T). They measure the percentage of cells in each phase of the cell cycle at a given time point, and test the effect of a CDK inhibitor drug on cell proliferation.
Cell Cycle Phase Distribution:
| G1: Line N 45% | Line T 18% |
|---|
| S: Line N 20% | Line T 47% |
| G2: Line N 15% | Line T 28% |
| M: Line N 10% | Line T 6% |
| G0: Line N 10% | Line T 1% |
A CDK (cyclin-dependent kinase) inhibitor is applied to both cell lines at the same concentration. After 48 hours, Line N shows a 12% reduction in cell number while Line T shows a 67% reduction.
Questions in This Drill
- Based on the table, which conclusion about Line T is most directly supported by the data?
- A researcher proposes that Line T cells are less responsive to internal checkpoint signals that would normally halt cell cycle progression. Which finding from the table is most consistent with this proposal?
- CDK inhibitors reduce cell proliferation by blocking cyclin-dependent kinases. Which mechanism best explains why Line T shows a greater reduction in cell number than Line N after CDK inhibitor treatment?
- A student argues that the CDK inhibitor would be a more effective cancer treatment if it could be modified to exclusively target cells in S phase. Which reasoning best evaluates this argument?
- In normal cells, the retinoblastoma protein (Rb) acts as a tumor suppressor by inhibiting progression from G1 into S phase. Which molecular event would most likely result in a cell cycle profile similar to Line T?