Down syndrome is a birth defect caused by a genetic disorder that affects 350,000 people in the United States. It is caused by abnormalities in the genes and is not inherited, meaning that parents do not pass this onto their children. In order to understand Down Syndrome, one must examine genetics of a ?normal? person as well as a person with Down Syndrome.
Genetics is the study of heredity, or how certain traits are passed from parents to their children. Genes are the basic unit of heredity while cells are the building blocks of your body. Each person has more than 100 trillion cells. Our genes are located in chromosomes. Each cell in your body contains 46 chromosomes or 23 pairs. In the case of a person with Down syndrome, there are 47 chromosomes. In 1956, a French researcher named Jerome Lejeune used a new powerful microscope to view human strands of DNA. DNA is what holds an individual person?s genes. He studied these DNA strands and determined that there is an extra strand in chromosome 21, which is now called ?Trisomy 21? tri meaning three and somy for the word chromosome ? meaning three chromosomes. No one knows exactly
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