Final answer:
Cystic fibrosis persists due to an autosomal recessive inheritance pattern and potential heterozygote advantages such as increased resistance to certain infections for carriers. Medical advancements have improved the life expectancy of those with CF, and carriers can unknowingly pass the mutation on to their children.
Step-by-step explanation:
Cystic fibrosis is a severe genetic disease that persists in the human population due to its autosomal recessive inheritance pattern. Carriers of one defective CFTR gene, who are often unaffected by the disease, can unknowingly pass the gene to their offspring.
Despite the significant health challenges posed by cystic fibrosis, advancements in medical treatments have helped increase the life expectancy of those affected. However, the persistence of this condition can be attributed to what's known as the heterozygote advantage, which suggests that carriers of the mutation may have increased resistance to certain infections, such as cholera or tuberculosis.
The CFTR protein's role is to transport Cl- ions out of the cells, which when malfunctioning due to mutations, leads to the production of abnormally thick and sticky mucus. This mucus buildup causes blockages in mucus-secreting organs, leading to respiratory infections and malabsorption of nutrients.
With approximately 1 in 25 individuals of Northern European ancestry being carriers, cystic fibrosis has a frequency of about 1/3000 births in the US. The disease illustrates an important concept in genetics, where the presence of a disease-causing allele can be maintained in a population due to a potential survival advantage it confers to heterozygous individuals.