Down syndrome is a genetic disorder, also known as trisomy 21. It occurs due to the presence of a third copy of chromosome no 21. Down syndrome is related to delays on physical growth and development, elemental facial trait and average intellectual abilities. This genetic disorder is the most commonly occurring chromosome abnormalities among humans (Epstein, 2013).The occurrence ratio is one in 1000 babies who are born every year. It has been found that the genetic disorder was prevalent among 8.5 million people that led to 36000 demise (Vos et al., 2015). The disorder was named after the British doctor, John Longdon Down. However, the French researchers discovered the cause of the disorder, which is inherited genetically. In this assignment, the basics of the genetic disorder with pedigree chart, new diagnostics and treatments of the disorders are discussed.
The Down syndrome is a persistent state caused by the extra copy of chromosome 21. The parents of Down syndrome affected children are normal atypically on context to genetics. The extra copy of the chromosome 21 occurs randomly by chance. It results when a complete or partial copy of the chromosome 21 is present. The chromosomes are the collection of genetic information present in every cell within the human body. Generally, 46 chromosomes present in human body are organized in 23 pairs of chromosomes. Among them, 22 pairs are known as autosomes and one pair referred to as sex chromosomes. However, in individuals with Down syndrome, an extra copy of the chromosome 21 is found and this condition is referred to as trisomy 21. Hence, such individuals have 47 chromosomes instead of 46 chromosomes. As a result, present of this three copies of chromosome 21 with genetic material leads to the occurrence of Down syndrome (Malt et al., 2013). The risk of being affected by the disorder increase from 0.1% among the 20 years old mothers to 3% within the mothers in the age group of 45 years (nads.org, 2016). Until date, there has not been found any activity related to behavioral patterns or environmental determinants that alter the risk of the occurrence of disorder. The individuals with this genetic disorder have some distinguishing facial as well as physical characteristics, medical complications and cognitive disabilities. The facial traits include upturned eyes, flat nose, small nose, small mouth with proportionally larger tongue and round face with flattened profile on a average. The physical features include small feet and short finger (Langlois et al., 2013). They have higher chances of developing medical complications. They have vision and hearing difficulties too. They are found with heart defects that might be mild or severe. In addition to the above mentioned issues, they might suffer from gastrointestinal problems, thyroid functioning, chances of developing cancer and mental illness. A pedigree chart for Down syndrome is a rough outlining of the likelihood of a child for developing with this condition because of the previous generations. Since, the Down syndrome is not an inherited disorder, so accurate diagram for predicting the chances of developing it is not possible. It occurs in case where a child possesses an extra copy of chromosome.
(Figure 1: Pedigree chart of Down syndrome)
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There are two types of tests available for Down syndrome, which can be done prior to the birth of a baby; they are screening tests and diagnostic tests. Though the screening tests do not provide information that the disorder would take place in the baby surely, however, it merely states the chances that a baby may develop such a disorder. Whereas, the diagnosis tests facilitate 100% accurate results and provide absolute diagnosis. A new screening technique is available for prenatal screening among the pregnant mothers. The blood tests help in measuring the amount of substances present in the mother’s blood. These tests help in estimating the chances of the mother to give birth to a baby with Down syndrome. Mostly, the screening tests include blood or serum tests and sonogram.. These advanced techniques are now available for detection of fetal chromosomes that circulates in mother’s blood. Unlike the diagnostic tests, these screening tests are non-invasive but give accurate results. The diagnostic tests that are available for prenatal detection of Down syndrome include Chronic Villus Sampling (CVS) as well as amniocentesis. These procedures although carry a risk factor of 1% chance of miscarriage, nevertheless these methodologies provide with 100% accurate diagnosis of Down syndrome. Amniocentesis is generally done during the second trimester of gestation period between 15 and 20 weeks, CVS is performed mostly between 9 and 14 weeks of pregnancy. The recognition of Down syndrome is generally performed at birth. It is detected by the presence of certain physical characteristics such as low tonality of muscles, a single crease in the palm are of the hand, flat profile, rounded face and upturned eyes. However, such traits are sometimes present in normal babies, so a chromosomal analysis is done referred to as karyotype in order to reaffirm the diagnosis. Generally, blood is drawn from cells of the baby for performing the karyotype.
The chromosomes are photographed. They are grouped according to their size, shape and number. In this way, the doctors diagnose Down syndrome by examination of the karyotype. There is another test for examining genetic disorders known as FISH. This is applied using the same principle as that of the karyotype for confirming the diagnosis for shorter time-period (Palomaki et al., 2012). Down syndrome is not curable. However, early interventions and treatment procedures may help the individuals to lead productive life. The treatments include exercises, speech and occupational therapy for improving the motor abilities. Special educational patterns and proper care with attention can help them further. The medical complications like hearing impairments, thyroid and related disorders can be corrected. Use of amino acid supplements as well as drugs like Piracetam that are believed to provide improved ability to apprehend and teach (Bartesaghi et al., 2015).
Down syndrome is one of the most commonly occurring genetic disorders that occur due to formation of an extra copy of chromosome 21. The distinctive traits of facial and physical characteristics are common in Down syndrome, which are used for detection of the disorder. The modern treatment and diagnostic procedures are however capable of detecting the disorder with accuracy. In this way, early detection can be helpful for treating such patients by speech therapy, exercises so that they can lead a prospective life. However, further advancement in the field of genetics will help in adding on to more technologies for detection, diagnoses and treatment of Down syndrome.
Bartesaghi, R., Haydar, T. F., Delabar, J. M., Dierssen, M., Mart?nez-Cu?, C., & Bianchi, D. W. (2015). New Perspectives for the Rescue of Cognitive Disability in Down Syndrome. The Journal of Neuroscience, 35(41).
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Langlois, S., Brock, J. A., Wilson, R. D., Audibert, F., Carroll, J., Cartier, L., ... & Okun, N. (2013). Current status in non-invasive prenatal detection of Down syndrome, trisomy 18, and trisomy 13 using cell-free DNA in maternal plasma. Journal of Obstetrics and Gynaecology Canada, 35(2).
Malt, E. A., Dahl, R. C., Haugsand, T. M., Ulvestad, I. H., Emilsen, N. M., Hansen, B., ... & Davidsen, E. M. (2013). Health and disease in adults with Down syndrome. Tidsskrift for den Norske laegeforening: tidsskrift for praktisk medicin, ny raekke, 133(3).
Palomaki, G. E., Deciu, C., Kloza, E. M., Lambert-Messerlian, G. M., Haddow, J. E., Neveux, L. M., ... & Nelson, S. F. (2012). DNA sequencing of maternal plasma reliably identifies trisomy 18 and trisomy 13 as well as Down syndrome: an international collaborative study. Genetics in medicine, 14(3).
Vos, T., Barber, R. M., Bell, B., Bertozzi-Villa, A., Biryukov, S., Bolliger, I., ... & Duan, L. (2015). Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013. The Lancet, 386(9995).
www.nads.org,. (2016). Facts About Down Syndrome- National Association for Down Syndrome. Retrieved 31 October 2016, from
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