2 Sex chromosome anomalies Sex Chromosome AbnormalitiesPattern / NameCharacteristicsIncidenceTreatmentXYYMale; tall stature; tendency to low IQ, especially verbal1 in 1,000 male birthsNo special treatmentXXX (triple X)Female; normal appearance, menstrual irregularities, learning disorders, mental retardation1 in 1,000 female birthsSpecial educationXXY (Kleinfelter)Male, sterility, underdeveloped secondary sex characteristics, small testes, learning disordersHormone therapy, special educationXO (Turner)Female, short stature, webbed neck, impaired spatial abilities, no menstruation, sterility, underdeveloped sex organs, incomplete development of secondary sex characteristics1 in 3,500 female birthsFragile XMinor-to-severe mental retardation; symptoms, which are more severe in males, include delayed speech and motor development, speech impairments, and hyperactivity; the most common inherited form of mental retardation1 in 1,200 male births; 1 in 2,000 female birthsEducational and behavioral therapies when needed
3 Sex chromosomes abnormalities KLINEFLETER SYNDROMEA male with XXY chromosomesExhibits some female characteristicsSuch as enlarged breasts andhigh pitched voiceTURNERS SYNDROMEA female with XO exhibits a short stature, short neck, and broad chest with immature sex organs
4 XYYIf in meiosis II the Y chromosome does not separate and is passed on to a boy the sex chromosomes will be XYY. Boys with this are unusually tall but have normal fertility. Studies have also shown that these men tend to be more violent than a XY male.
5 How does it happen? Non-disjunction can result in abnormalities in the number ofsex chromosome. Both Klinefelterand Turners result from nondisjunctionof either the male or female gamete.The disjunction of the female gametescan result in a Triple X female
6 Down SyndromeDown syndrome is a chromosomal abnormality of the 21th chromosome. It is known as Trisomy 21 since nondisjunction of a faulty cell division results in an embryo with three number 21 chromosomes instead of two. People with down syndrome are usually mentally retarded, shorter, have a larger head and a short life span (usually about 30 years).
7 Down syndrome- Prior to, or at, conception, a pair of number 21 chromosomes, in either the sperm or the egg, fail to separateKaryotype of down syndrome