Down's Syndrome
Epidemiology
Trisomy 21
1 in 800
Aetiology
Advanced maternal age
- 1/ 50 mothers > 45
- however mothers < 30 still most common
Genetics
- 95% non disjunction during meiosis
- 4% are result of translocation (Chr 21 joins to Chr 14)
- 1% are mosaics