Autosomal recessive disorders comprises nearly one third of single gene diseases. For autosomal recessive diseases to be functional, a single gene couple at the same locus must be functionally modified together. Autosomal recessive diseases may not be observed in each generation and family pedigree shows a horizontal pattern. Parents are generally healthy and disease is observed in siblings of index cases within the same generation. Consanguineous marriages increase the risk of incidence, because partners of consanguineous marriage are coming from a common ancestor with a higher risk of having the same mutant gene in their genomes.
The disease does not show gender discrimination and the degree of strike remains the same. The risk of disease to arise is 25% for carriers in each pregnancy. As the probability of being carrier for the kids is 50% in recessive diseases, only by 25% of chance that the kids do not have mutant gene. When a carrier marries a normal person or the one carrying no mutant gene, there is no risk for the disease to occur. If the patient marries a normal person, all of the kids will be healthy but be carrier. If a patient marries a carrier, the risk of becoming ill and carrier will be 50% for each pregnancy.