Biology Forums - Study Force

The familial form of retinoblastoma is characterized by cancer appearing in both eyes relatively early in life. In contrast, the sporadic form is usually unilateral and appears later. What accounts for the difference?
 
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Individuals with the familial form inherited one retinoblastoma mutation. The addition of another mutation early in life is likely to result in bilateral retinoblastoma. The sporadic form of retinoblastoma requires two mutations in the same cell and is therefore less likely to occur bilaterally.