First in Genetics
Last updated: September 2026
A fun way to remember key genetics milestones: several landmark "firsts" in human genetics happen to have their prototype disease in ophthalmology. (Original list credit: Alex Levin, MD, Wills Eye/CHOP.)
| Category | First described disease |
|---|---|
| 1st Autosomal Dominant (AD) | Piebaldism |
| 1st Autosomal Recessive (AR) | Alkaptonuria |
| 1st X-linked Recessive (XR) | Red-green color deficiency |
| 1st X-linked Dominant (XD) | Incontinentia pigmenti |
| 1st Mitochondrial | Leber Hereditary Optic Neuropathy (LHON) |
| 1st Digenic inheritance | Retinitis pigmentosa (specific RP loci) |
| 1st Trigenic inheritance | Bardet-Biedl syndrome |
| 1st "Two-hit hypothesis" tumor | Retinoblastoma (Knudson, 1971) — see our Retinoblastoma Genetics page for the modern application of this model |
| 1st Contiguous gene deletion syndrome | WAGR syndrome (Wilms tumor, Aniridia, Genitourinary anomalies, Range of developmental delay) — deletion at chromosome 11p13 |
Why this list is genuinely useful, not just trivia
Each of these represents a landmark moment where studying an eye disease directly advanced the entire field of human genetics — not just ophthalmology:
- Retinoblastoma and the two-hit hypothesis: Alfred Knudson's 1971 statistical analysis of retinoblastoma incidence patterns (comparing hereditary bilateral cases to sporadic unilateral cases) established the foundational concept of tumor suppressor gene inactivation requiring two separate "hits" — a framework that now underlies our understanding of essentially all hereditary cancer syndromes, not just RB
- LHON and mitochondrial inheritance: among the first human diseases conclusively mapped to mitochondrial DNA mutations, establishing that mitochondrial genetics follows maternal inheritance patterns distinct from Mendelian rules
- WAGR and contiguous gene deletion syndromes: demonstrated that a single chromosomal deletion spanning multiple adjacent genes could produce a combination of seemingly unrelated features — a concept now central to understanding many microdeletion syndromes
Key reference: Knudson AG. Mutation and cancer: statistical study of retinoblastoma. Proc Natl Acad Sci USA. 1971;68(4):820-823.
📘 Want the exam-ready deep dive? This topic, and much more is covered in Ophthalmology Explorer (A High-Yield Clinical Reference for Ophthalmology Residents, Fellows & Board Exams) — available on Kindle. See all my books.
Experiencing symptoms like these? Learn about our Eye Department or book a consultation with Dr. Dhaval Patel.