Question

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
inversion
deletion
insertion

Answer 1

The type of chromosomal mutation that causes Down syndrome, specifically the common form resulting from an extra chromosome 21, is **nondisjunction**. Nondisjunction occurs when chromosomes fail to separate properly during cell division, leading to a gamete with an extra chromosome. When this gamete contributes to the formation of an embryo, it results in trisomy 21, which is the genetic condition associated with Down syndrome.