Saturday, October 18, 2008

Syndrome

Down’s syndrome

A person with Down’s syndrome has three copies of chromosome 21, rather than the usual two. The ratio of this syndrome is about 1 in 800 live births. Individuals with Down’s syndrome usually have multiple physical malformations, mental retardation and relatively short lives. They typically have short, stocky bodies with thick hands and feet. They also commonly have broad, short heads with small low-set ears, small concave saddle-shaped or flattened nose, relatively large-ridged tongues that roll over a protruding lower lip, low muscle tone and loose joints.

Turner’s syndrome

Basically it occurs on female with only one X chromosome. Therefore the genotype is XO. This syndrome is relatively rare and it is about 1:2500 live births. Turner’s syndrome is a chromosomal condition that affects girls and women. It is characterized by short stature, webbed neck and triangular face, lack of menstruation, undeveloped secondary sexual characteristics and infertility.

Klinefelter’s syndrome

It occurs when an individual, normally male, has two X and one Y chromosomes. The individual will have a relatively high-pitched voice, increased breast tissue and comparatively little facial and body hair. They are normally sterile or subfertile. Their testes and prostate glands are small therefore, they produce small amount of testosterone. They mostly overweight, have difficulties in learning and have short term memories. There is about 1 in 500 and 1 in 1000 male births.

XYY syndrome

The individual will have an extra copy of the Y chromosome. They are normally male and also called as “super-male”. During adolescence, they are often slender, have severe facial acne and poorly coordinated. They are usually fertile and lead ordinary lives as adults. As adult, they will grow above 6 feet tall and generally appear and act normal. However they produce high levels of testosterone. There is about 1 in 900 or 1 in 2000 male birth.

XXX syndrome

The individual will have three X chromosomes and is also called as “super-female”. They are usually an inch or so taller than average. They have long legs and slender torsos. Their sexual characteristics are normal but they may have slight learning difficulties and are usually in the lower range of normal intelligence. The frequency of birth is 1 in 1000 female infants and it occurs more commonly when the mother is older.

Biology Oxford Fajar

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