a woman has the inherited form of retinoblastoma (rb). her husband does not have rb, and they have monozygotic (identical twins) twin girls. one girl got rb before the age of 5, and her twin avoided rb throughout her entire childhood. how is this possible? please choose the correct answer from the following choices, and then select the submit answer button. answer choices both girls inherited the rb mutation, but in one girl, the inherited normal copy of the rb gene suffered a somatic mutation that led to rb, and the other girl did not suffer a somatic mutation in her normal copy of the gene. both girls inherited the rb mutation but, in one girl, a defect occurred in a mismatch repair gene which led to a number of somatic mutations in several tumor-suppressor genes and proto-oncogenes, and eventually rb developed. both girls inherited the rb mutation, but in the girl that did not suffer from rb, a back mutation occurred in the mutated rb gene somatically that resulted in the restoration of the wild-type allele. one girl inherited the rb mutation from the mother and the other girl didn't.