Down syndrome (DS) is considered to be the most common genetic disorder. It is caused by the presence of a partial or complete duplicate of chromosome 21 and is otherwise known as trisomy 21. Down syndrome is characterized by slower than usual physical and mental development, and consequently, a mental disability, as the average IQ of an affected individual is 50, which is about a half of the average for a genetically normal young adult (www #1). The disease is a result of overexpression of 310 genes, and as a randomly occurring disorder, it is neither recessive nor dominant and is not linked to a gender-defining chromosome (23rd pair).
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The disorder is easily recognizable from the characteristic facial features and is congenital as it forms during fetal development (www #2). Usually, the parents of a child with DS are genetically normal, and the disorder occurs by chance. Factors like age contribute to the risk of having an affected baby, as it rises to 3% for 45-year-old mothers (www #3). The disease is discoverable through prenatal screening or genetic testing, and frequently, pregnancies are terminated once DS has been discovered.
Down syndrome is uncurable, but family support and education can improve the life quality of an affected individual. In some cases, children with DS have completed schools and even attended a university; many do some form of paid work but often require special conditions. The disease occurs most frequently in populations where abortion is considered unethical. There is not an evident global leader in the number of the affected individuals as not all cases are documented, but the United States registry cites an average of 0.14% of all the population being affected by DS (www #4).
Turner syndrome, although incurable, can be treated using various methods of contemporary medicine. As a gender-linked disorder, birth control is commonly used to develop sexual characteristics, the hormonal support of which is vital for the maintenance of healthy bones, heart, and other tissues. Moreover, modern methods of reproduction are used for TS-affected females who want to have a baby. Overall, treatment methods improving life quality are widely available.
Around thirty percent of TS-affected women suffer from a webbed neck (extra skin folds), lymphedema (swelling of limbs), skeletal development defect, lower than normal hairline, and kidney issues (www #5). Other features are a wide chest, receding jaw, crossed or lazy eyes, and drooping eyelids. Usually, affected females have normal intelligence although they can possess learning disabilities, and have trouble orienting in space. Sometimes, social situations can also become difficult, although a little record of this has been discovered (www #6).
The disorder is not inheritable, and in rare cases caused by chromosome abnormalities such as ring chromosome or isochromosome X. The former happens when the long and short arms of a broken chromosome join to form a ring, while the latter is a result of a replacement of one missing arm with an identical copy of the other arm. In essence, Turner Syndrome is the opposite of Down syndrome in terms of chromosomal development.
There are other diseases similar to Turner Syndrome. One of those is the Noonan syndrome, a congenital disorder that also results in a webbed neck, facial abnormalities, widely set eyes, and other developmental changes. In contrast to TS, Noonan syndrome affects both genders and occurs as a result of mutations in the tauopathy pathway. It is a multiple-gene disorder affecting less than 0.1% of the population (www #6).
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Revised estimates of the maternal age specific live birth prevalence of Down’s syndrome, 2002, Sage Journals. Web.
Updated national birth prevalence estimates for selected birth defects in the United States, 2004–2006 – Parker – Birth Defects Research Part A: Clinical and Molecular Teratology – Wiley Online Library. Web.
Turner syndrome – Genetics Home Reference – NIH. Web.
Turner Syndrome – NORD (National Organization for Rare Disorders). Web.