The fact that ma means "what" when used as an interrogative doesn't mean it has anything to do with how the morpheme [ma] modifies the verb דַע to create the meaning of "knowledge".Isaac Fried wrote:Here is another example for the stringing of personal pronouns to create words out of roots. From spoken Hebrew: דַע DA, 'know', מַדָע=מה-דע, MA-DA, 'science', literally, 'what-know'; מַדָעִי=מדע-היא, MADAIY, 'scientific', literally, it-science'; מַדָעָן=מה-דע-אן, MADAAN, 'scientist m.'; מַדָעָנִית=מה-דע-אן-היא-את, 'scientist f.'; מַדָעִים=מה-דע-הם, 'sciences'.
Isaac Fried, Boston University
As for מַדָעִי there is nothing to connect the yod suffix to the female pronoun היא. Neither is there any argument for how the semantic value "she" might inform the root and change it from a noun to an adjective.
Jonathan Mohler