Final answer:
A genetic disorder is a disease caused by a mutation in one or more genes or by a chromosomal alteration. Down syndrome is caused by an extra copy of chromosome 21. Inherited mutations play a role in 5 to 10 percent of all cancers.
Step-by-step explanation:
A genetic disorder is a disease, syndrome, or other abnormal condition caused by a mutation in one or more genes or by a chromosomal alteration. An example of a genetic disorder is cystic fibrosis. A mutation in a single gene causes the body to produce thick, sticky mucus that clogs the lungs and blocks ducts in digestive organs.
Down syndrome is caused by having three copies of chromosome 21, known as trisomy 21. The most common cause of trisomy 21 is chromosomal nondisjunction during meiosis. The frequency of nondisjunction events appears to increase with age, so the frequency of bearing a child with Down syndrome increases in females over 36.
Inherited mutations are thought to play a role in about 5 to 10 percent of all cancers. Specific mutations that cause many of the known hereditary cancers have been identified. Most of the mutations occur in genes that control the growth of cells or the repair of damaged DNA.