Turner Syndrome Monosomy of X Chromosome (X0) Most girls are born with two X chromosomes, but girls with Turner syndrome are born with only one X chromosome or they are missing part of one X chromosome. Girls with Turner syndrome are usually short in height. Girls with Turner syndrome who aren't treated reach an average height of about 4 feet 7 inches (1.4 meters). In addition to growth problems, Turner syndrome prevents the ovaries from developing properly, which affects a girl's sexual development. Because the ovaries are responsible for making the hormones that control breast growth and menstruation, most girls with Turner syndrome will not go through all of the changes associated with puberty unless they get treatment for the condition. Nearly all girls with Turner syndrome will be infertile, or unable to become pregnant on their own. Cry of the Cat - "Cri du Chat" Deletion of Part of Upper Arm of Chromosome 5 Cri-du-chat syndrome was first described by Lejeune et al. (1963) as a hereditary congenital syndrome associated with deletion of part of the short arm of chromosome 5. Cri-du-chat syndrome is characterized in young children by microcephaly, round face, hypertelorism, micrognathia, epicanthal folds, low-set ears, hypotonia, and severe psychomotor and mental retardation. One of the most characteristic features in newborn children is a high-pitched cat-like cry that is usually considered diagnostic for the syndrome. Patau's Syndrome Trisomy of Chromosome 13 Edward's Syndrome Trisomy of Chromosome 18 Down Syndrome Trisomy of Chromosome 21 This is a mild to severe form of mental retardation accompanied by distinctive physical traits. People with Down syndrome have an irregularity with autosome pair 21. In most cases, there is an extra chromosome (i.e., trisomy). Down syndrome individuals typically have short, stocky bodies with thick hands and feet. Their hands commonly have a simian crease, which is a crease in the palm that runs completely from one side of the hand to the other. In addition, they usually have broad, short heads with small low-set ears, small concave saddle-shaped or flattened noses, relatively large ridged tongues that roll over a protruding lower lip, low muscle tone, and loose joints. Klinefelter Syndrome Trisomy of 23rd Pair (XXY) Having 2X and 1Y chromosome Males inherit one or more extra X chromosomes--their genotype is XXY or more rarely XXXY, XXXXY, or XY/XXY mosaic. They characteristically have relatively high- pitched voices, asexual to feminine body contours as well as breast enlargement, and comparatively little facial and body hair. They are sterile or nearly so, and their testes and prostate gland are small. As a result, they produce relatively small amounts of testosterone. The feminizing effects of this hormonal imbalance can be significantly diminished if Klinefelter syndrome boys are regularly given testosterone from the age of puberty on. Like metafemales (described above), many Klinefelter syndrome men are an inch or so above average height. They also are likely to be overweight. They usually have learning difficulties as children, especially with language and short-term memory. Trisomy of 23rd Pair (XYY) Having 1 X & 2 Y chromosomes Males inherit an extra Y chromosome--their genotype is XYY. As adults, these "super- males" are usually tall (above 6 feet) and generally appear and act normal. However, they produce high levels of testosterone. During adolescence, they often are slender, have severe facial acne, and are poorly coordinated. They are usually fertile and lead ordinary lives as adults. Many, if not most, are unaware that they have a chromosomal abnormality.
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