Down Syndrome

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Down Syndrome

Down syndrome is the most common genetic disorder among children. 1 out of every 1,000 is diagnosed with what is more commonly known as DS (Leshin, 2000). DS was first observed in 1866 by John Langdon Down, an English physician. However, only speculation existed on what caused this debilitating disease. In 1959, Jerome Lejeune and Patricia Jacobs discovered the true cause. It is trisomy of the 21st chromosomes that causes DS and the debilitating characteristics along with it (Leshin, 2000).

Chromosomes are string like structures that contain DNA and other compounds. They are the information center of living organisms. DNA can be broken down into smaller parts called genes, which contain traits of the individual. A human cell has forty six chromosomes, which can be grouped into 23 pairs. However, in sex cells, the sperm and egg [gametes] only contain 23 chromosomes. This happens because of a cell division process called meiosis, where one cell splits into two cells, each containing half the original cell’s DNA. It is during this process where complications can occur (Leshin, 2000).

During meiosis the chromosomes, after forming a tetrad, separate and go to opposite sides, to form alleles. This is called disjunction. This event does not always happen with 100% accuracy. In some cases a chromosome does not split and still moves to one side. Therefore, the resulting mutation, called nondisjunction, causes one of the two gametes to have an extra chromosome; one having twenty four and the other twenty two chromosomes. When the mutated sperm or egg fertilizes a normal gamete of 23 chromosomes, it results in an egg with an abnormal number of chromosomes. 95% of all cases of DS result from th...

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...e you and I. Through research, government funding, and their tenacious will, they are living normal and healthy lives. They are getting married, finding jobs, and competing in athletics. The debilitating affects of Down’s syndrome no longer hold these people to sheltered lives. They deserve the rights and respect of every other human being.

Works Cited

Berg, Linda R., Diana W. Martin, Edlra P. Solomon. Biology. Ed. Nedah Rose. 6th ed. USA: Thomas Learning Inc., 2002.

Leshin, Len MD, FAAP. “Trisomy 21: The Story of Down Syndrome.” Down Syndrome: Health Issues. 2000. 14 October 2003 <>

CChem, Lubec G., Dr., FRSC. Riverbend Down Syndrome Parent Support Group. 19 March 2003

Selikowitz, Mark. Down Syndrome The Facts. New York: Oxford University. 29-66
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