2121 2121 八 Disjunction of chromosome 21 IOSIS 2121 gamete 21 21 21 212121 21 212121 oosperm 21 monosomy 21-trisomy Pathogenesis of standard type 2/-tr chromosome 2/ duri21 21 21monosomy 21-trisomy Pathogenesis of standard type 21-trisomy:disjunction of chromosome 21 during miosis Disjunction of chromosome 21 21 21 21 21 21 Germ cells 21 21 21 21 0 21 21 gamete 21 21 21 oosperm miosis