In Sporadic Cases of Retinoblastoma,only Two Gene Mutations Are Thought

In sporadic cases of retinoblastoma,only two gene mutations are thought to be necessary in the same cell for a tumor to develop.This happens when an organism inherits a mutant allele and a wild- type allele forms the parents.When the wild- type allele is mutated,resulting in tumorigenesis,this process is called,_______ .

A) gain of heterozygosity
B) loss of heterozygosity
C) recombination
D) metastasizing
E) attenuation