What is unusual about the inheritance of retinoblastoma, given that it appears to be inherited as a dominant trait?

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Quizplus · Accepted Answer

Despite being inherited as a dominant trait, not all children who inherit the RB deletion gene develop retinoblastoma. This is due to the phenomenon of incomplete penetrance, which means that not all individuals carrying a disease-causing gene mutation will necessarily develop the associated disease. In the case of retinoblastoma, it is estimated that only around 90% of individuals with the RB deletion gene will develop the cancer.

What Is Unusual About the Inheritance of Retinoblastoma, Given That