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Question:

Bill and Bob are biological twins who were adopted as babies. Their adoptive father and his father and his father (Billy and Bob’s father, paternal grandfather, and paternal great-grandfather) all suffered from early-onset fingernail greening. Which of the following statements is most likely to be the case?

A Being adopted, it’s unlikely that Bill or Bob are at risk.
Explaination

We know from the prompt that Bill and Bob are adopted so, they do not share their genetics with their adoptive father. It’s also very likely, since three generations of the males in the family of their adoptive father have green nails, that the disease is a genetic trait, rather than one determined by their environment.