9th Grade, College Bound Biology
Duncansville, PA
  Printed with the permission of the author

Down Syndrome is also (or formally) known as mongolism, and is the most frequent chromosomal abnormality in the United States. Over 350,000 people carry this condition.
It is caused by an extra 21st chromosome. This is also known as trisomy 21. Instead of 46 chromosomes in each cell it was determined that an extra 21st chromosome affected Down syndrome, this occurs 95% of the time. There are three copies of this chromosome. It is causes by a cell error called non-disjunction. Two other types are mosaicism and translocation. Non-disjunction causes faulty cell division and produces three copies of the 21st chromosome instead of two. Either the sperm or the egg don't separate during division causing the extra chromosome to replicate in every cell. As stated above it is responsible for 95% of Downs.
Mosaicism is when non-disjunction occurs in one cell division after fertilization causing a mixture of two types of cells. Some of these cells contain 46 chromosomes others contain 47 chromosomes. This type of Down syndrome is very rare and is less affected. Mosaicism is responsible for 1-2 percent of Downs.
The last type of Down syndrome is translocation. This occurs when part of the 21st chromosome breaks off during cell division and attaches to another chromosome. The total number of chromosomes is still 46, yet an extra part causes the certain features of down syndrome. This is also very rare and is responsible for 3-4% of Downs.
In the 19th century, John Langdon Down was an English physician who published an accurate description of a person with Down syndrome. Published in 1888 he was considered the "father of the syndrome".
Down syndrome has many appearances different from a normal person. A person with this condition may have a small skull, short flat nose; also known as flat facial profile, short fingers and neck, small almond shaped eyes; they also show small skin folds on the inner core of the eye (known as Epicanthal folds), oblique palpebral fissures is also know in the eye for it's upward slant, plus an enlargement of the tongue. Some other characteristics are simian crease which is a single deep crease across the palm of the hand, and there is an excessive space between the large toe and second toe. When born a child may seem "floppy."
Some of the medical defects are ear infections (result from mild to moderate hearing loss), speech difficulty, respiratory problems, obstructed digestive tract, a child has a greater risk of getting leukemia (a cancer), and heart problems. There also is a lack of muscle tone know as muscle hypotonia, a mild to moderate retardation, and some of the retardation is in growth and development. In other words, a child is slower to walk and learn. In adults there is a greater possibility of Alzheimer's disease.
In the development period of a person with Down syndrome they need special care. They can learn to sit and walk, talk, play, toilet train, and do other normal activities. They do show hearing and speech difficulties; therefore, need special classes. Around 80% show hearing loss which also leads to the speech development as well as an academic progress.
The hearing loss is usually from the flattened ear that Down syndrome people have. It doesn't catch sound effectively and is easily blocked by dry skin or wax.
People with this condition may sometimes have seizures. These can be noticed by the jerking of the arms and legs, and maybe sometimes they'll loose conciousness. Also, one might just loose attention and go into a lapse. The age of a mother may also be a factor in this genetic disorder. A mother that is older (for example 48) may have a 1 in 12 chance of getting a baby with Downs. If a mother is younger (30) they have a 1 in 900 chance of having a baby with the condition. There is a 1 in 800 live births of babies with the disorder.
To detect Down syndrome there are two types of procedures to a pregnant woman. A screening test, which measures the quantity of substances in the blood. This has only a 60% accuracy. Another type of detection is the diagnostic test. This may cause a miscarriage due to tissue being taken from the umbilical cord. Examining to the babies chromosomes this test is 98 to 99% accurate. There is no cure for this disease, yet there are medicines to help with the symptoms that a person might have or encounter.
There are many other factors of Down syndrome and research. NDSS, National Down Syndrome Society, sent some pamphlets and you may view them. To contact them or get more information call or write:
666 Broadway
New York, NY 10012-2317