Genetic Disorders

The two most common aneuploidies, trisomies and extra sex chromosomes, can be due to maternal or paternal factors including advanced age. A number of aneuploidies can be attributed to dispermy, or when two sperm fertilizes one egg. The resulting genetic disorders can result in a spontaneous mutation. Live-born children with autosomal aneuploidies can have trisomy 13, 18, or 21, and all have some form of developmental delay, while trisomy of any other chromosome is usually always fatal. Trisomy 13 (Patau's syndrome) is characterized by retarded growth, cleft lip, small head and chin, and often polydactyly. Trisomy 18 (Edward's syndrome) is marked by severe, variable abnormalities of the head, thumbs, ears, mouth, and feet. Trisomy 21 (Down's syndrome) occurs equally in all ethnic groups, and is closely related to increased maternal age.

Aneuploidy of the sex chromosomes can cause abnormal genital development, sterility, and other growth problems. The most common aberrations involve multiple X chromosome syndromes. Males with an XXY aneuploidy have Klinefelter's syndrome, and have small testes and typically no sperm. Hermaphrodites are individuals that have both male and female genitals, are extremely rare, and result from cell lines that have two different chromosome patterns with both XX and XY cells.