Chromosomal mutations can have a variety of effects on individuals. Down syndrome is a disorder that causes problems such as mild to moderate mental retardation and slow or stunted development. A common form of this disorder is the result of a genetic mutation that occurs when there is an extra chromosome 21. Which type of chromosomal mutation causes this form of Down syndrome?
Nondisjunction occurs when chromosomes fail to separate properly during cell division, so a cell can receive an extra chromosome. The form of Down syndrome described involves three copies of chromosome 21, so the correct choice is nondisjunction.
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