Down syndrome most commonly occurs due to ____
Down&;s syndrome occurs due to nondisjunction in maternal meiosis. Down&;s syndrome: Most common chromosomal disorder Incidence: 1/800 live bihs Mechanism: Trisomy 21 (meiotic maternal nondisjunction) (95%) Robesonian translocation: 4% Mosaic pattern: 1% Non-disjunction points to the failure of the homologous chromosome to seperate during the meiotic division. Ref: Nelson textbook of pediatrics 21st edition Pgno: 658
Reciprocal translocation
Non-disjunction in maternal meiosis
Mosaicism
Non-disjunction in paternal meiosis
Growth and development