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Turner syndrome is characterized by a collection of symptoms, including short stature, webbed neck, and incomplete or absent development of secondary sex characteristics, leading to infertility.
Although Turner syndrome is seen in about 1 in 2,500 to 1 in 5,000 female live births, the 45, X karyotype accounts for 10 to 20 percent of the chromosomal abnormalities seen in spontaneously aborted fetuses, demonstrating that almost all 45, X conceptions are lost to miscarriage.
Human genetic disease, any of the diseases and disorders that are caused by mutations in one or more genes.
With the increasing ability to control infectious and nutritional diseases in developed countries, there has come the realization that genetic diseases are a major cause of disability, death, and human tragedy.
Although the biochemical basis of numerical chromosome abnormalities remains unknown, maternal age clearly has an effect, such that older women are at significantly increased risk to conceive and give birth to a chromosomally abnormal child.
Chromosome disorders can be grouped into three principal categories: (1) those that involve numerical abnormalities of the sex chromosomes.
Autosomes are the 22 sets of chromosomes found in all normal human cells.
The risk increases with age in an almost exponential manner, especially after age 35, so that a pregnant woman age 45 or older has between a 1 in 20 and 1 in 50 chance that her child will have trisomy 21 (Down syndrome), while the risk is only 1 in 400 for a 35-year-old woman and less than 1 in 1,000 for a woman under the age of 30.
There is no clear effect of paternal age on numerical chromosome abnormalities.