"Do you respect my grandfather?"
Translation:Czy wy szanujecie mojego dziadka?
First at all - there is no genitive in this sentence.
Genitive in Polish is used:
- with negation instead of accusative
- after certain verbs
- after certain prepositions
- to indicate possession
- in some other rare situations
Masculine "animated" nouns in singular, and masculine personal nouns in plural have accusative=genitive.
my house= Nom. mój dom (masc. not animated)= Acc. mój dom-- Gen. mojego domu
my grandpa = Nom. mój dziadek (masc. animated)-- Acc. mojego dziadka=Gen mojego dziadka
It does mean Genitive, and Genitive is one of the two cases which have a form 'mojego', but there's no way (at least for now) to make Duolingo show only hover tips that relate to a specific sentence. "Dom mojego dziadka" = "My grandfather's house" is indeed Genitive, but here it's Accusative, like immery has said before.
Moral of the story: don't trust hover tips that much, they show possible translations which are dependent on a context, and not only it's possible that some of these won't have a usage in a given sentence, but sometimes even none of them may be useful because it shows maximum 3.