zoom in with enumerated list in beamer

Question

I would like to create an enumerated list, with some more details on a second slide. What I try is the following

Slide A

1 First
2 Second
3 Third

However, on slide B I would like to display

1 First
2 Another topic before Second
3 Yet another topic before Second
4 Second
5 Third

It should be displayed, that item number 2 on slide A is the same than topic number 4 on slide B. It would be nice to get fancy replys.

Answer 1

This works:

\documentclass{beamer}
    \begin{document}
        \begin{frame}
            \begin{enumerate}
                \item First
                \only<2->{
                \item Another topic before Second
                \item Yet another topic before Second}
                \item Second
                \item Third
            \end{enumerate}
        \end{frame}
    \end{document}

But I recommend this instead, agreeing with AlexG:

\documentclass{beamer}
    \begin{document}
        \begin{frame}
            \begin{enumerate}
                \item First
                \item<2-> Another topic before Second
                \item<2-> Yet another topic before Second
                \item Second
                \item Third
            \end{enumerate}
        \end{frame}
    \end{document}