Why can Cystic fibrosis be inherited even if neither parent has the disease?

Answer 1

Cystic Fibrosis is an example of a disease inherited as an autosomal recessive genetic disorder. Both parents of a baby who has Cystic Fibrosis have one abnormal recessive gene and one normal dominant gene and are therefore, Cystic Fibrosis carriers. Carriers are said to be heterozygous because they contain one normal copy of the gene and one abnormal copy. A baby who inherits cystic fibrosis has inherited the abnormal gene from both parents and is therefore said to be homozygous recessive.

Answer 2

Cystic fibrosis can be inherited even if neither parent has it because it is carried by a recessive allele. If both parents have this recessive allele it is possible that the child will get the disease.