Which of the following is an example of an autosomal recessive disorder?

Cystic fibrosis is an example of an autosomal recessive disorder because it is caused by mutations in both copies of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which is located on an autosome (specifically chromosome 7). In autosomal recessive disorders, a person must inherit two copies of the mutated gene, one from each parent, to express the disease. If an individual only has one copy of the mutated gene, they are considered a carrier and typically do not show symptoms of the disorder.

In contrast, Huntington's disease is an autosomal dominant disorder, meaning that a single copy of the mutated gene (from one parent) is sufficient to cause the disease. Hemophilia is typically inherited in an X-linked recessive pattern, primarily affecting males since they have one X chromosome. Down syndrome, or trisomy 21, is caused by an extra chromosome and does not follow the autosomal recessive inheritance pattern either. Therefore, cystic fibrosis stands out as the clear example of an autosomal recessive disorder among the provided options.