Question

In cystic fibrosis, two unaffected carriers can have a child with the disease. It is as common in boys as in girls. This disease is

A. autosomal dominant.
B. X-linked recessive.
C. autosomal recessive.
D. X-linked dominant.
E. pleiotropic.

Answer 1

Cystic fibrosis is classified as an autosomal recessive genetic disorder, which means a child must inherit two copies of the defective gene to be affected. It is equally common in both males and females as the CFTR gene is located on an autosome, not a sex chromosome.

Step-by-step explanation:

Cystic fibrosis is an autosomal recessive disorder. Both male and female offspring have an equal chance of inheriting the disease if both parents are carriers.

Cystic fibrosis (CF) is characterized by the production of thick mucus in the lungs and digestive tract, leading to chronic respiratory and digestive issues. This genetic disorder is caused by mutations in the CFTR gene, which is located on chromosome 7, an autosome, meaning it is not linked to sex chromosomes. Thus, it affects males and females equally. For a child to have cystic fibrosis, they must inherit two copies of the defective gene, one from each parent. When both parents are carriers, there is a 25% chance of having a child with the disease. This follows Mendelian inheritance patterns observed by Gregor Mendel, which state that for an autosomal recessive trait, a 3:1 ratio of unaffected to affected offspring is expected when both parents are carriers (heterozygous for the trait). With advancements in medical intervention, individuals with CF can now live into middle adulthood, despite the challenge it poses to health.

Since the inheritance of cystic fibrosis is not influenced by the sex of the offspring, and it follows an autosomal recessive inheritance pattern, the correct answer is C. autosomal recessive.