This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics And Genetic Disorders, Subject name: Pediatrics
The population frequency for phenylketonuria is 1 in 10,000. What is the carrier frequency for the disease? 
Select and explain. 
A. Jan-50, B. 1/100, C. 1/500, D. 1/1000
A: Jan-50
Answer: A: Jan-50 
Explanation: a. 1/50(Ref: Nelson's 20/e p 598)It is based on Hardy Weinberg principle: Simplifying it,Carrier frequency for an autosomal recessive disorder = twice the square root of disease incidenceSo 2 X square root of 1/10,000 gives 1/50 as the answer.