Give an example of a homozygous recessive genetic disorder.
One example of an autosomal recessive disorder is Cystic Fibrosis. Since Cystic Fibrosis is a recessive disease, in order to have the disease a person must inherit two copies of the recessive allele for the gene named CFTR. Cystic Fibrosis causes cells to not be able to transport salt in and out properly. This results in a build up of mucus on the outside of the cells, and it affects the lung cells the most. The lungs get clogged with mucus which not only affects breathing, but also causes them to become easily infected. Because of this, without treatment people with Cystic Fibrosis generally have shortened lifespans.
As a recessive disorder, people who are heterozygous, and therefore carry one copy of the recessive allele, are carriers. They do not have the disease, but they can pass on their one recessive allele to children. If they have a child with someone who is also a carrier, there is a 25% chance of their child having Cystic Fibrosis. If instead they have a child with someone who is homozygous dominant for the CFTR gene, there is no chance that their child will have Cystic Fibrosis. This is why people who have a family history of Cystic Fibrosis may choose to consult a genetic counselor to determine the chances of passing on the disease to their children.