Final answer:
A genetic disorder can be caused by a single abnormal gene from either parent. An example is cystic fibrosis, which is caused by a mutation in a single gene that leads to the production of thick, sticky mucus.
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. Some genetic disorders are caused by mutations in just one gene, which can come from either parent. These disorders are known as Mendelian genetic disorders. An example is cystic fibrosis, which is caused by a mutation in a single gene that leads to the production of thick, sticky mucus. This disorder can be inherited from either the mother or the father.