Down syndrome (trisomy 21) is the most common chromosomal disorder and the most common genetic cause of intellectual disability, occurring in ~1:700 live births. The risk increases with advanced maternal age (>35 years), but most babies with Down syndrome are born to mothers under 35 because they have more pregnancies overall. Cause: Extra copy of chromosome 21 - Nondisjunction (95% of cases): extra chromosome from failed meiotic division - Translocation (4%): extra chromosome 21 material attached to another chromosome - Mosaicism (1%): milder; only some cells have trisomy 21 On the exam, writers often pair stable-sounding options with unstable data—notice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan: breathing work and oxygenation, perfusion and end organs, neuro baseline, likely infection sources, and devices that can fail quietly. When two answers feel partly right, pick the one that reduces imminent harm and matches orders for the role you were given. Train yourself to state the primary...