what is autosomal recessive

Autosomal recessive is a pattern of inheritance where two copies of an abnormal gene must be present in order for a disease or trait to develop. Genes come in pairs, and one gene in each pair comes from the mother, and the other gene comes from the father. Recessive inheritance means both genes in a pair must be abnormal to cause disease. People with only one defective gene in the pair are called carriers. These people are most often not affected with the condition, but they can pass the abnormal gene to their children. If both parents carry the same autosomal recessive gene, their child has a 25% chance of inheriting the abnormal gene from both parents and developing the disease, a 50% chance of inheriting one abnormal gene and becoming a carrier, and a 25% chance of inheriting two normal genes. Autosomal recessive disorders can be caused by mutations in genes located on one of the first 22 nonsex chromosomes. Examples of autosomal recessive disorders include cystic fibrosis, sickle cell anemia, and Tay-Sachs disease.