If transmission of genetic information from cell to cell is normally achieved by copying the complementary DNA molecules how is this information equally shared between two daughter cells?

Cystic fibrosis is a disease that occurs when an individual carries two copies of a recessive version of a membrane transport gene. A person that is a carrier for cystic fibrosis (that means they carry one copy of the gene that causes cystic fibrosis but their other copy is normal - they do not have cystic fibrosis) has a child with another person that is also a carrier for cystic fibrosis. What is the probability that this couple has three children that do not have cystic fibrosis AND are also not carriers of cystic fibrosis? 0.25 0.422 0.016 2.25 0.75