Biology College question

Question

In 40% of cases of retinoblastoma, a predisposition to developing the cancer is inherited (as in the pedigrees above). However, in 60% of cases of retinoblastoma, the cancer occurs sporadically (the first case in a family) and children of these patients do not necessarily inherit a predisposition for retinoblastoma. What is the same about these two situations? What is different?

Answer 1

Hi Monica A.,

So what would be wrong with assuming that the mutation(s) inheritable retinoblastoma is(are) present ab initio in the embryo, hence in every cell of the baby (and perhaps associated with a predisposition to other forms of cancer as well?), whereas the non-inheritable one is a mutation at a later stage of development, such that only tissue of one eye is affected? (all you need for the latter is just one sufficiently mutated cell, after all, and possibly immune system disfunction to a degree). I leave it for you to work out the details.

-- Cheers, -- Mr. d.