Cystic fibrosis is a hereditary disease that affects the respiratory and digestive systems. cystic fibrosis occurs when two recessive genes (cc) are present. a person with one allele for cystic fibrosis is called a carrier (cc) of the disease. if the mother is a carrier of the disease and the father is homozygous dominant, what are the chances that their first child will be a carrier of cystic fibrosis?