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Difficulty: MediumGenetic and Molecular Mechanisms

Match each patient's clinical presentation and family history to the underlying genetic and molecular mechanism most likely responsible for their condition.

  • A 35-year-old woman with early-onset breast cancer and a strong family history of ovarian and pancreatic cancers.Defective homologous recombination repair of double-strand DNA breaks.
  • A 42-year-old man with a mucinous, right-sided colon carcinoma and a family history of endometrial cancer.Impaired recognition and repair of DNA nucleotide mismatches.
  • A 24-year-old man with hundreds of adenomatous polyps found on colonoscopy and a family history of early-onset colorectal cancer.Loss of regulation in the Wnt/beta-catenin cellular signaling pathway.
  • A 28-year-old woman with early-onset breast cancer who previously survived childhood osteosarcoma.Inactivation of a key transcription factor responsible for arresting the cell cycle to allow DNA repair.

Answer

1. BRCA1/2 presentation matches defective homologous recombination. 2. Lynch syndrome presentation matches impaired mismatch repair. 3. FAP presentation matches loss of Wnt/beta-catenin regulation. 4. Li-Fraumeni presentation matches inactivation of a cell cycle-arresting transcription factor.
Each pairing correctly links a distinct hereditary cancer syndrome's clinical manifestation to its precise underlying molecular and genetic pathogenesis.

Step-by-Step Solution

1
Analyze the first clinical presentation (early-onset breast cancer, family history of ovarian/pancreatic cancers).
Identify this as Hereditary Breast and Ovarian Cancer syndrome (BRCA1/2 mutations).
Recognizing the syndrome is required to determine the molecular defect.
2
Analyze the second clinical presentation (right-sided mucinous colon cancer, family history of endometrial cancer).
Identify this as Lynch syndrome (Hereditary Nonpolyposis Colorectal Cancer).
Lynch syndrome is associated with specific DNA repair defects.
3
Analyze the third clinical presentation (hundreds of colonic polyps in a young patient).
Identify this as Familial Adenomatous Polyposis (FAP).
FAP is driven by a distinct molecular pathway compared to other colon cancers.
4
Analyze the fourth clinical presentation (childhood osteosarcoma and early-onset breast cancer).
Identify this as Li-Fraumeni syndrome (TP53 mutation).
Multiple early-onset primary tumors in a specific pattern are a hallmark of this syndrome.
5
Match each identified syndrome to its known genetic and molecular mechanism.
BRCA = Homologous recombination; Lynch = Mismatch repair; FAP = Wnt/beta-catenin pathway; Li-Fraumeni = p53 transcription factor.
Connecting the clinical phenotype directly to the molecular defect.

Key Concept

Molecular pathogenesis of inherited cancer susceptibility syndromes.
Estimated Time:1m 30s
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Topics

Genetic and Molecular Mechanisms

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