This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
Regarding retinoblastoma all of the following are true, EXCEPT: 
Select and explain. 
A. 13q14p mutation, B. Autosomal dominant, C. 25% Bilateral, D. 40% Heritable forms
C: 25% Bilateral
Answer: C: 25% Bilateral 
Explanation: Hereditary retinoblastoma accounts for 40% of cases. All bilateral and cases and about 15% of the unilateral cases are hereditary. Retinoblastoma gene has been identified as 14 band on the long-arm of chromosome 13 (13q14). Deletion or inactivation of this protective gene by two mutations results in occurrence of retinoblastoma. Inheritance is autosomal dominant and the risk of transmitting the gene mutation is 50%. Because of high penetrance 40% of offspring of a surviver of hereditary retinoblastoma will develop the tumor. 33% are bilateral (1/3rd cases). Ref: Ophthalmology by A K Khurana 4th edition, Page 280