Rabiatul Adawiah Binti Hashim Dietetics 3

Definition  Down syndrome is a genetic disorder and the most usual autosomal chromosome abnormality in humans at which extra genetic material from chromosome 21 is transferred to a newly formed embryo.  These extra genes and DNA cause changes in development of the embryo and fetus that give results in mental and physical abnormalities.  Down syndrome may causes lifelong mental retardation, developmental delays and other problems. Down syndrome varies in severity so that developmental problems range from moderate to serious.

Symptoms  Flattened facial features  Small head  Short neck  Protruding tongue  Upward slanting eyes  Unusually shaped ears  Poor muscle tone  Broad, short hands with a single crease in the palm  Relatively short fingers  Excessive flexibility  Infants with average size, grow slowly and remain shorter than other children of similar age

Causes Down syndrome is usually caused by an error in cell division called nondisjunction. Nondisjunction results in an embryo with 3 copies of chromosome 21 instead of the usual 2. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate. As the embryo develops, the extra chromosome is replicated in every cell of the body. This type of Down syndrome accounts for 95% of cases. Trisomy 21 Mosaicism occurs when nondisjunction of chromosome 21 takes place in one but not all of the initial cell divisions after fertilization. When this occurs, there is a mixture of two types of cells, some containing the usual 46 chromosomes and others containing 47. Those cells with 47 chromosomes contain an extra chromosome 21. Mosaicism accounts for about 1% of all cases of Down syndrome. Mosaic Down syndrome Translocation accounts for about 4% of all cases of Down syndrome. In translocation, part of chromosome 21 breaks off during cell division and attaches to another chromosome, typically chromosome 14. While the total number of chromosomes in the cells remain 46, the presence of an extra part of chromosome 21 causes the characteristics of Down syndrome. Translocation Down syndrome

Risk Factors Advancing maternal age Having had one child with Down syndrome Being carriers of the genetic translocation for Down syndrome

Complications Heart defects Dementia Sleep apnea ObesityLeukemia Infectious diseases

Coping and Support Don't believe misinformation about Down syndrome Find a team of trusted professionals Seek out other families who are dealing with the same issues

References  Mayo Clinic Staff. Disease and Conditions Down syndrome. (2011). Retrieved from conditions/down-syndrome/basics/ on January 5th, conditions/down-syndrome/basics/  National Down Syndrome Society. What Is Down Syndrome? (2012). Retrieved from Down-Syndrome/ on January 5th, Down-Syndrome/  Benjamin Wedro, Charles Patrick Davis. Down Syndrome. (2013). Retrieved from overview/article.htm on January 5th, overview/article.htm

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