Chromosomal abnormalities manifest themselves in two ways 2 )Defects in newborns: 0.5% aggregate frequency among the most common XXY 1/1.000 males XYY /1.100maes 0双 1/7,500 females /1.200 females Trisomy 13 1/1500 Trisomy 18 1/1100 Trisomy 21 1/900 Structural anomalies 1/4002) Defects in newborns: 0.5% aggregate frequency Among the most common: XXY XYY XO XXX Trisomy 13 Trisomy 18 Trisomy 21 Structural anomalies 1 / 1,000 males 1 / 1,100 males 1 / 7,500 females 1 / 1,200 females 1 / 15,000 1 / 11,000 1 / 900 1 / 400 Chromosomal abnormalities manifest themselves in two ways: