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 1/1,100 males XO 1/7,500 females XXX 1/1,200 females Trisomy 13 1/15,000 Trisomy 18 1/11,000 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: