<prompt> Cystic fibrosis is inherited as an autosomal recessive condition. A normal couple has one daughter affected with the disease. They are now planning to have another child. What is the chance of her sibling being affected by the disease -02-Jan4-Jan4-Mar  <response>: Ans. is. c i.e., 14 o The fact that one child of a normal couple is affected by an autosomal recessive condition cystic fibrosis indicates that both parents are carriers of this condition. o The recurrence risk of autosomal recessive disorders in siblings is 25 for each bih. Both the parents are carrier -- 25 children will be affected, 50 will be carrier and 25 will be normal. o From above flow cha it is clear that with each bih :? i One chance in four been affected 25, i.e. the risk of recurrence is 25 for each bih. ii Two in four chance to being normal but a carrier 50 iii One in four chance of being normal and unaffected 25 iv Three in four chances of being phenotypically normal 75, i.e. not manifesting disease 