Patau's syndrome (Trisomy 13) results from the presence of three copies of chromosome 13 ($2n + 1 = 47, +13$). It causes severe intellectual disability, cleft lip/palate, polydactyly, heart defects, and neural tube defects. Median survival is less than one week; 90% of affected infants die within the first year. Trisomy 18 = Edwards syndrome; Trisomy 21 = Down syndrome; Trisomy 22 = cat-eye syndrome or Emanuel syndrome.