A patient has a brother with sickle cell disease and she is planning a family. She does not have the condition. Assuming the population carrier frequency is 1 in 100, what is the chance of her child having the disease?
- 1 in 25
- 1 in 1200
3. 1 in 600 - 1 in 150
- 1 in 10
solution
Sickle cell disease is autosomal recessive. Her brother must have inherited both of the affected genes. She has a 2 in 3 chance of being a carrier. If her and her partners are carriers then there would be a 1 in 4 chance of the child being affected. You multiply the the probabilities to get 2 over 1200, therefore 1 in 600.