What is an autosomal recessive (AR) disease?
AR conditions require that an individual with the disease inherits two deleterious mutations in the same gene, one from each genetic parent. Carriers have just one abnormal mutation and are not affected. Currently most people do not know whether or not they are carriers. Family genetic and medical history is of limited value in assessing the risk of AR diseases because the chance of a match between two carriers for CF is only 1 in 841. Therefore, screening for carriers of AR diseases is a clear example of how new technology can provide would-be parents with information which may influence their reproductive choices. The inheritance of AR diseases follows the classic Mendelian patterns you may remember from your high school biology class. When both partners are carriers, 1 in 4 children inherit two defective genes and have the disease; half of the offspring inherit one defective gene and thus are unaffected carriers; 1 in 4 children inherit two normal genes. If only one partner is a car
