Learning Objectives
- Map major genetic disorders to their specific chromosomes for rapid recall.
- Identify chromosomes that house tumor suppressor genes and blood-related mutations.
- Master the “High-Yield” chromosome clusters (e.g., Chromosomes 13, 15, and 17).
1. Master Chromosome Map
The USMLE frequently tests the chromosomal location of specific genes. Use this organized table for categorization and memorization.
| Chromosome | Selected Examples | Memory Hook |
|---|---|---|
| 3 | VHL (von Hippel-Lindau), Renal Cell Carcinoma. | VHL = 3 letters. |
| 4 | Huntington disease, Achondroplasia, ADPKD (PKD2). | Huntington (4 letters in “Hunt”). |
| 5 | Cri-du-chat, FAP (Familial Adenomatous Polyposis). | Cri-du-chat (Deletion of 5p). |
| 6 | Hemochromatosis (HFE). | HFE gene. |
| 7 | Cystic Fibrosis, Williams syndrome. | CFTR on Chromosome 7. |
| 9 | Friedreich ataxia, Tuberous Sclerosis (TSC1). | TSC1 = 9. |
Activity
2. The “Heavy Hitters” (11 through 22)
| Chr. | Diseases | Clinical Context |
|---|---|---|
| 11 | Wilms tumor, β-globin defects (Sickle cell, β-thal), MEN1. | β is the 2nd letter, but β-globin is on 11. |
| 13 | Patau syndrome, Wilson disease, RB1, BRCA2. | Retinoblastoma and Wilson’s. |
| 15 | Prader-Willi / Angelman, Marfan syndrome. | Imprinting disorders center here. |
| 16 | α-globin defects, ADPKD (PKD1), TSC2. | PKD1 is on 16 (dominant form). |
| 17 | NF1, BRCA1, TP53 (Li-Fraumeni). | Major tumor suppressors (p53). |
| 22 | NF2, DiGeorge syndrome (22q11). | NF2 = Chromosome 22. |
Activity
3. Sex Chromosomes (X)
- Fragile X Syndrome: (CGG) expansion.
- Turner Syndrome (XO): Monosomy X.
- Klinefelter Syndrome (XXY): Aneuploidy.
- XLA: Bruton agammaglobulinemia.
Activity