Molecular diagnostics · USMLE Step 1

Which statement correctly distinguishes molecular genetic tests from cytogenetic tests?

  1. Molecular tests find chromosome-number changes; cytogenetics finds point mutations
  2. Molecular tests examine DNA sequences; cytogenetics examines chromosome structure
  3. Molecular tests measure proteins; cytogenetics measures membrane lipids
  4. Molecular tests always use antibodies; cytogenetics always uses fluorescent probes
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Correct answer: Molecular tests examine DNA sequences; cytogenetics examines chromosome structure

Molecular genetic tests focus on specific genes or DNA sequences (point mutations, small deletions or insertions), whereas cytogenetic tests examine large-scale chromosomal structure or number to detect gross chromosomal abnormalities.

Difficulty: Medium Question 7 of 21

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