If two normal parents have a cystic fibrosis child (normal as in not suffering from CF) ,this means that they are both carriers as cystic fibrosis is a recessive disorder and the sufferer is pure breeding recessive ( homozygous recessive ) for CF. All this info. Tells us that the parents both have the normal allele and also the abnormal allele in their genotypes. Both parents genotypes are therefore heterozygous for CF. Both are heterozygotes for CF.
