Autosomal and Sex chromosome abnormalities

Sex chromosome anomalies

Sex Chromosome Abnormalities

Pattern / Name Characteristics Incidence Treatment

XYY Male; tall stature; tendency to low IQ, especially verbal

1 in 1,000 male births

No special treatment

XXX(triple X)

Female; normal appearance, menstrual irregularities, learning disorders, mental retardation

1 in 1,000 female births

Special education

XXY(Kleinfelter)

Male, sterility, underdeveloped secondary sex characteristics, small testes, learning disorders

1 in 1,000 male births

Hormone therapy, special education

XO(Turner)

Female, short stature, webbed neck, impaired spatial abilities, no menstruation, sterility, underdeveloped sex organs, incomplete development of secondary sex characteristics

1 in 3,500 female births

Hormone therapy, special education

Fragile X Minor-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 retardation

1 in 1,200 male births;1 in 2,000 female births

Educational and behavioral therapies when needed

Sex chromosomes abnormalities

KLINEFLETER SYNDROMEA male with XXY chromosomesExhibits some female characteristicsSuch as enlarged breasts and high pitched voice

TURNERS SYNDROME

A female with XO exhibits a short stature,

short neck, and broad chest with immature

sex organs

XYY

If 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.

How does it happen?

Non-disjunction can result in abnormalities in the number of sex chromosome. Both Klinefelterand Turners result from nondisjunctionof either the male or female gamete.The disjunction of the female gametes can result in a Triple X female

Down Syndrome Down 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).

Down syndrome- Prior to, or at, conception, a pair of number 21 chromosomes, in either the sperm or the egg,

fail to separate

Karyotype of down syndrome