Introduction:

Disorders of Sex chromosome are generally milder than defects of autosomes. They lead to fewer problems. In fact, sex chromosome disorders are often not recognized until adolescence, when, in some of the deviations, puberty is delayed. The most common problems involved the presence of an extra chromosome (either X or Y) or the absence of on X chromosome in females. Sometimes, individuals inherit more than one extra chromosome, as in XXXX, XXXY or XYYY. Defects tend to become more severe as genetic material is added.
The Sex chromosomal disorders include XYY Syndrome, Triple X (XXX) Syndrome, Klinefelter Syndrome (XXY), Turner Syndrome (XO) and Fragile X Syndrome.
Studies of children with Triple X, Klinefelter, and Turner Syndrome reveal that adding to subtracting from the usual number of X Chromosomes leads to specific intellectual problems. Fragile X syndrome is a major genetic cause of mental retardation.
A variety of myths about individuals with sex chromosome disorders exit. For example, many people think that males with XYY syndrome are more aggressive and anti-social than XY males. Yet by examining we will see that this is not true. Also, it is widely believed that children with sex chromosome disorders are retarded. Yet most are not. The intelligence of boys with XYY Syndrome is similar to that of normal children and the intellectual problems of children with Triple X, Klinefelter and Turner Syndromes are very specific. Verbal difficulties (for example, with reading and vocabulary) are common among girls with triple X syndrome and boys with Klinefelter syndrome, each of whom inherited and extra X chromosome. In contrast, Turner Syndrome girls, who are missing an X, have trouble with spatial relationships. Their handwriting is poor, and they have difficulty telling right from left and finding their way around the neighborhood during the early school years. When they get to high school, they avoid courses like geometry and those that demand drawing skills.

a) XYY Syndrome:
Cause: Inheritance of an extra Y chromosome.
Typical Characteristics – above average in height, large teeth, and sometimes severe acne.
Intelligence, development of male sexual characteristics, and fertility are normal.
For this disorder, no special treatment is necessary.

b) Triple X Syndrome (XXX): super female syndrome
Cause: Inheritance of an extra X chromosome.
Typical characteristics- impaired verbal intelligence.
Affected girls are no different in appearance or sexual development from normal age mates, except for a greater tenderness towards tallness.
- Impaired verbal intelligence and poorer memory for recent events.
Treatment:
Special treatment is necessary to treat verbal ability problems.

C) Klinefelter Syndrome (XXY)
Cause: Inheritance of an extra X chromosome.
Characteristics:
- Impaired verbal intelligence.
- Affected boys are unusually tall, have a body in which fat distribution resembling females and show incomplete development of sexual characteristics at puberty.
- They are usually sterile. They have underdeveloped testes- less of testerone.
- They have poor muscular development
- Their cognitive functioning and personality mildly retarded.

Treatment:
- Hormone therapy at puberty will help to stimulate the development of sexual characteristics.
- Special education can be given to treat verbal-ability problems.
- Carrier detection, prenatal detection, amniocenteses and chronic villus sampling is possible.

d) Turner Syndrome (XO)
Reason: All or part of the second X chromosome is missing

Characteristic:
- Ovaries usually do not develop prenatal.
- Incomplete development of sexual characteristics at puberty. They have impaired spatial intelligence. Other features include short stature and webbed neck. They have physical abnormalities
- They may be mentally retarded and sexually underdeveloped.

Treatment:
- Hormone therapy in childhood will help to stimulate physical growth and at puberty to promote development of sexual characteristics.
- Special education can be provided to treat Spatial-ability problems

Characteristics:
- It is associated with mental retardation and mild facial deformities including enlarged ears, jaw and forehead.
- About 12% have infantile autism (a serious bizarre, self –stimulating behaviour and delayed or absent language and communication).
- They have broad nasal route
- Enlarged testicles in males.
- Some have normal IQ, but others have learning disabilities, difficulties with frontal lobe and right hemisphere tasks.

Treatment:
Special therapeutic programme can be given for retarded and behavior disordered children.




Bibliography:

Berk.E. Laura, Child development, New Delhi: Prentice Hall of India Private Limited, 2001