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

Robbins basic pathology 9th edition page no 220, heading=disorders of Autosomal recessive inheritance Siblings have one chance in four of being affected. Therefore the chance of the sibling being affected according to the question is 1/4.