Chromosomal abnormalities · USMLE Step 1

A woman with multiple miscarriages is found to carry a balanced Robertsonian translocation. What is her chromosomal composition?

  1. 45 chromosomes with one fused chromosome
  2. 47 chromosomes with one extra chromosome
  3. Normal chromosome number but structural rearrangement
  4. Both homologs of a chromosome inherited from one parent
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Correct answer: 45 chromosomes with one fused chromosome

Robertsonian translocation carriers have 45 chromosomes due to fusion of two acrocentric chromosomes. They are usually phenotypically normal but have reproductive risks. The other options describe different chromosomal outcomes.

Difficulty: Medium Question 9 of 20

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