Cystic fibrosis is a fatal genetic disease that affects one child in 1,600. it is an autosomal recessive gene. both parents are heterozygous for this trait. a9) what are the phenotypes of each parent?

Normal phenotype (no disease)

Explanation:

According to the given information, cystic fibrosis is an autosomal recessive disease which means that the gene for the disease is present on the autosome and is recessive. Being recessive in nature, the disease is expressed only in homozygous recessive genotype while the individuals with homozygous dominant genotype do not express the disease.

The individuals with heterozygous dominant genotype are carriers for the disease but do not express the disease. Let's assume that the gene "a" causes the disease while the dominant allele "A" imparts normal phenotype. The genotype of the heterozygous parents would be "Aa". Being heterozygous, the parents would not be affected by the disease and would have a normal phenotype.  

a symbiotic relationship with the mitochondria