All of the following statements are true regarding retinoblastoma, except:

Rb gene Governor of the cell cycle Negative regulator of the G1/S cell cycle transition. Located on 13q14 chromosome. To explain the two patterns of occurrence of retinoblastoma, Knudson proposed "two hit" hypothesis of oncogenesis. Two mutations (hits), involving both alleles of RB at chromosome locus 13q14, are required to produce retinoblastoma. Familial variant is autosomal dominant in inheritance.