an explanation for the bilateral, and earlier, occurrence of hereditary retinoblastoma; if one tumor suppressor gene is mutated by inheritance, only one somatic mutation is needed inactivate the other allele. In the sporadic form, two mutations, which inactivate each allele, are necessary.
[Alfred G. Knudsen, contemporary U.S. geneticist]
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Examples: glitazone, GI cocktail, etc.