5. What is the correct description of the genotype for individuals that express the trait cystic fibrosis?

heterozygous.

heterozygous recessive

homozygous recessive

heterozygous dominant

homozygous dominant

homozygous recessive

Explanation:

Cystic fibrosis is a recessive genetic disorder. It means that the trait is caused due to the presence of a recessive allele. The recessive alleles are expressed only in homozygous recessive genotypes. Individuals that express the disorder cystic fibrosis should have two copies of a recessive allele of the gene, that is, the genotype should be homozygous recessive.

If "C" allele is the normal healthy allele and "c" allele is cystic fibrosis allele, the genotype of the affected individual would be "cc".