Which of the following statements best describes a characteristic of oncogenes? (A) All retroviruses contain at least one oncogene. (B) Retroviral oncogenes were originally obtained from a cellular...

Which of the following statements best describes a characteristic of oncogenes?

(A) All retroviruses contain at least one oncogene. (B) Retroviral oncogenes were originally obtained from a cellular host chromosome. (C) Proto-oncogenes are genes, found in retroviruses, that have the potential to transform normal cells when inappropriately expressed. (D) The oncogenes that lead to human disease are different from those that lead to tumors in animals. (E) Oncogenes are mutated versions of normal viral gene products.