e d g e
- education for disability and gender equity
3. Additional chromosomes
In some cases entire chromosomes, or large segments of them, are missing, duplicated, or otherwise altered. Down Syndrome and Turner's Syndrome are examples of this type of disorder. The extra chromosome creates differences that make people recognizable by physical traits in common.
One type of Down Syndrome results when three, rather than the normal two, copies of chromosome 21 are present in each cell (trisomy 21).
An unusual number of chromosomes results when a mistake called nondisjunction occurs in the production of eggs or sperm. Whereas in most cases three copies of a chromosome are lethal to the embryo, in certain cases an extra or missing chromosome is tolerated.
Individuals with an extra chromosome often have serious medical problems due to the imbalance in gene products expressed from that chromosome.
In the case of Down Syndrome, trisomy 21 may cause any of a series of potential developmental delays, characteristic facial features, and decreased muscle tone, resulting in wide range of intellectual and physical abilities.
it is a common disability, as a society we have a lack of awareness
about it. People with Down Syndrome face discrimination based on the
way the look and misunderstandings about their disorder. (Genetic
Science Learning Center, University of Utah).