Down Syndrome

Topics: Down syndrome, Chromosomal translocation, Chromosome Pages: 5 (1631 words) Published: February 16, 2014

Down Syndrome is a congenital disorder arising from a chromosome It comes from a defect involving chromosome 21. The condition leads to impairments in both cognitive ability and physical growth that range from mild to moderate developmental disabilities. Through a series of screenings and tests, Down syndrome can be detected before and after a baby is born. 

The only factor known to affect the probability of having a baby with Down syndrome is maternal age. Less than one in 1,000 pregnancies for mothers less than 30 years of age results in a baby with Down syndrome. For mothers who are 44 years of age, about 1 in 35 pregnancies results in a baby with Down syndrome. Because younger women generally have more children, about 75 - 80% of children with Down syndrome are born to younger women. Cause of Down Syndrome

Down syndrome occurs because of an abnormality characterised by an extra copy of genetic material on all or part of the 21st chromosome. There are normally 46 chromosomes in each cell, 23 inherited from your mother and 23 from your father. When some or all of a person's cells have an extra full or partial copy of chromosome 21, the result is Down syndrome. 

The most common form of Down syndrome is known as Trisomy 21, a condition where individuals have 47 chromosomes in each cell instead of 46. This is caused by an error in cell division called nondisjunction, which leaves a sperm or egg cell with an extra copy of chromosome 21 before or at conception. Trisomy 21 accounts for 95% of Down syndrome cases, with 88% originating from nondisjunction of the mother's egg cell.  (Robertsonian) Translocation Down syndrome occurs when part of chromosome 21 becomes attached (translocated) onto another chromosome (usually chromosome 14), before or at conception. Children with translocation Down syndrome have the usual two copies of chromosome 21, but they also have additional material from chromosome 21 attached to the translocated chromosome. This form of Down syndrome is uncommon. Mosaic Down syndrome (or mosaicism) is a rare form of Down syndrome, in which children have some cells with an extra copy of chromosome 21. This mosaic of normal and abnormal cells is caused by abnormal cell division after fertilsation.

Indications of people with Down syndrome
Individuals with Down syndrome often have distinct physical characteristics, unique health issues, and variability in cognitive development. Physical characteristics include: Eyes that have an upward slant, oblique fissures and white spots on the iris Low muscle tone

Small physique and short neck
Flat nasal bridge
Single, deep creases across the center of the palm
Protruding tongue
Large space between large and second toe
Relatively short fingers
Excessive flexibility
Individuals with Down syndrome usually have some degree of mental retardation, most often in the mild to moderate range. Children with Down syndrome often have a speech delay and require speech therapy. In addition, fine motor skills are delayed and tend to lag behind gross motor skills and may take more time (up to 4 years) to learn to walk. Prevalence Of Down Syndrome

Down syndrome is the most common chromosome disorder that we know of. One of every 700-900 babies born worldwide will have Down syndrome. This number has not changed a lot throughout the entire time that statistics have been collected. Down syndrome is not a new condition. People with Down syndrome have been recorded throughout history. An estimated 250,000 people in the United States have this condition. Although women of any age can have a child with Down syndrome, the chance of having a child with this condition increases as a woman gets older.

Is it inherited?
Down Syndorme is not ‘contagious’ as it is a genetic disease and resides in the very DNA and chromosome structure that are in the nucleus of our cells. Most of the time, Down syndrome isn't inherited. It's caused by a mistake in...

Bibliography: Down Syndrome: Switching Off Extra Chromosome Could Lead to a Cure. 2013. Down Syndrome: Switching Off Extra Chromosome Could Lead to a Cure. [ONLINE] Available at: [Accessed 06 September 2013]. 1950. Down Syndrome Australia - What is Down syndrome?. [online] Available at: [Accessed: 6 Sep 2013].
 Medical News Today. 2013. What Is Down Syndrome? What Causes Down Syndrome?. [online] Available at: [Accessed: 6 Sep 2013]. 2013. Australia Down Syndrome Clinical Research Study • Compose21. [online] Available at: [Accessed: 6 Sep 2013]. 2011. Down syndrome: Causes - [online] Available at: [Accessed: 6 Sep 2013]. 1979. CDC Data & Statistics | Feature: Down Syndrome Cases at Birth Increased. [online] Available at: [Accessed: 6 Sep 2013 2013. Down syndrome reversed in newborn mice with single injection - ABC News (Australian Broadcasting Corporation). [online] Available at: [Accessed: 6 Sep 2013]. 2013. down syndrome - Google Search. [online] Available at: [Accessed: 6 Sep 2013].
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