abnormal chromosome effects

Definition

Abnormal sex chromosome constitutions, such as XXX, XXY, XO, in fertilized eggs containing too many or too few sex chromosomes. People with XXX (triple-X or X-trisomy) chromosome constitution have the appearance of normal females but are called superfemales (some will be fertile); the XO (one X but lacking a Y) chromosome constitution are also females in appearance but remain immature (See: Turner's syndrome); XXY have enough Y chromosomal influence to look like males but have small testes and do not produce spermatozoa (See: Klinefelter's syndrome). More abnormal and rarer genetic anomalies such as XXXY, XXXXY, XXYY result in Klinefelter's syndrome and mental retardation.
See also: XXX; X-trisomy; XXY; XO; XXYY; XXXXY.