Cystic fibrosis is a genetic condition that affects the movement of salt and water in and out of cells, leading to a build-up of thick, sticky mucus in the lungs and digestive system.
The condition is caused by a recessive allele.
Explain what is meant by the term recessive allele.
Individuals who carry only one copy of the recessive allele do not show symptoms of cystic fibrosis. Suggest why this makes it difficult to reduce the number of children born with the condition.
A woman who is heterozygous for cystic fibrosis has a child with a man who is also heterozygous.
Use a genetic diagram to show the genotypes of these parents, the gametes they produce, and the genotypes and phenotypes of any possible offspring.
Use the letter FFF for the dominant allele and fff for the recessive allele.
Explain what is meant by the term gene mutation.
