Chorionic villi sampling testing or amniocentesis and karyotyping detects a Down syndrome child. Down syndrome child has tendency for leukemia, cataracts, faster aging, and mental retardation. XYY males with Jacob syndrome have two Y chromosomes instead of one. Earlier claims that XYY individuals were likely to be aggressive are not correct. Klinefelter syndrome males have one Y chromosome and two or more X chromosomes.
Individuals have large hands and feet and long arms and legs.
Triplo-X females have three or more X chromosomes. May experience menstrual irregularities, including early onset of menopause. Occurs in females, but symptoms are less severe. Passes from symptomless male carrier to grandson. Punnett square provides phenotypic ratio if all sperm are given equal chance to fertilize all eggs.