Aneuploidy(非整倍性) Trisomy(三体): three copies 47XY+2 1: Down syndrome Monosomy(单体): one copy 45, X: Turner syndrome Nondisjunction(不分离): failure of a pair of chromosomes to separate(to disjoin) normally in meiosis I or Il
Aneuploidy（非整倍性） • Trisomy（三体）: three copies – 47,XY+21: Down syndrome • Monosomy （单体） : one copy – 45,X: Turner syndrome • Nondisjunction（不分离）: failure of a pair of chromosomes to separate (to disjoin) normally in meiosis I or II
Different Consequences to the gamete of Nondisjunction at Meiosis i or meiosis ii MEIOSIS I Normal Nondisjunction Normal MEIOSIS‖ normal Normal Normal Normal Normal Nondisjunction both parental 2 copies of one 2ls present parental 21
Different Consequences to the Gamete of Nondisjunction at Meiosis I or Meiosis II both parental 21s present 2 copies of one parental 21
Abnormal male aryotype 47,XY+21 2 6 8 10 11 12 14 15 17 18 ?53 19 20 21 22 X
Abnormal Male Karyotype: 47,XY +21
Down syndrome Most common trisomy 1: 800 in new born Most common sever mental retardation Related with advanced maternal age
Down syndrome • Most common trisomy 1:800 in new born • Most common sever mental retardation • Related with advanced maternal age