A tumor shows loss of heterozygosity at chromosome 17p13. This mutation most likely inactivates which tumor suppressor gene, and what is its normal function?

• A RB1; controls G1-S checkpoint via E2F transcription factor
• B APC; regulates Wnt signaling by degrading beta-catenin
• C BRCA1; repairs double-strand DNA breaks by homologous recombination
• D TP53; acts as guardian of genome by halting cell cycle and inducing apoptosis in response to DNA damage ✓

Explanation

TP53 is located at chromosome 17p13 and is the most commonly mutated gene in human cancers. p53 acts as a transcription factor that induces CDKN1A (p21), DNA repair genes, and pro-apoptotic genes in response to genotoxic stress. RB1 is on chromosome 13q14. APC is on 5q21. BRCA1 is on 17q21.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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