I'm a new/beginner on tikz-qtree package, and trying to draw the straight line from F under R to T (level 2). Another problem, it not easy to use command \only{...}, how to use \only{...} in the better way.
\documentclass{beamer}
\usepackage{tikz-qtree}
\begin{document}
\begin{frame}
\begin{tikzpicture}[level distance=1.5cm, sibling distance=0.5cm]
\tikzset{grow'=up,frontier/.style={distance from root=150pt}}
\only<1>{
\Tree [.\mbox{ } \edge[draw=none];
[.\mbox{ } \edge[draw=none]; [.\mbox{ } \edge[draw=none]; [.$T$
\edge[draw=none]; $(P$ ] \edge[draw=none]; [.\mbox{ } \edge[draw=none];
$\wedge$ ] \edge[draw=none]; [.$T$ \edge[draw=none]; $Q)$ ] ]
\edge[draw=none]; $\vee$ \edge[draw=none]; [ \edge[draw=none]; [.$F$
\edge[draw=none]; $R$ ] ] ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; $\leftrightarrow$ ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; [.\mbox{ }
\edge[draw=none]; [.$\sim F$ \edge[draw=none]; $(\sim R$ ] ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; [.\mbox{ }
\edge[draw=none]; $\wedge$ ] ] \edge[draw=none]; [.\mbox{ }
\edge[draw=none]; [.$\sim T$ \edge[draw=none]; $\sim Q)$ ] ] ]
]
}
\only<2>{
\Tree [.\mbox{ } \edge[draw=none];
[.\mbox{ } \edge[draw=none]; [.$T$ [.$T$ \edge[draw=none]; $(P$ ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; $\wedge$ ] [.$T$
\edge[draw=none]; $Q)$ ] ] \edge[draw=none]; $\vee$ \edge[draw=none]; [
\edge[draw=none]; [.$F$ \edge[draw=none]; $R$ ] ] ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; $\leftrightarrow$ ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; [.$T$ [.$\sim F$
\edge[draw=none]; $(\sim R$ ] ] \edge[draw=none]; [.\mbox{ }
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; $\wedge$ ] ]
\edge[draw=none]; [.$F$ [.$\sim T$ \edge[draw=none]; $\sim Q)$ ] ] ]
]
}
\only<3>{
\Tree [.\mbox{ } \edge[draw=none];
[.$T$ [.$T$ [.$T$ \edge[draw=none]; $(P$ ] \edge[draw=none]; [.\mbox{ }
\edge[draw=none]; $\wedge$ ] [.$T$ \edge[draw=none]; $Q)$ ] ]
\edge[draw=none]; $\vee$ [ [.$F$ \edge[draw=none]; $R$ ] ] ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; $\leftrightarrow$ ]
\edge[draw=none]; [.$F$ [.$T$ [.$\sim F$ \edge[draw=none]; $(\sim R$ ] ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; [.\mbox{ }
\edge[draw=none]; $\wedge$ ] ] [.$F$ [.$\sim T$ \edge[draw=none]; $\sim Q)$ ] ] ]
]
}
\only<4>{
\Tree [.\alert{$F$}
[.$T$ [.$T$ [.$T$ \edge[draw=none]; $(P$ ] \edge[draw=none]; [.\mbox{ }
\edge[draw=none]; $\wedge$ ] [.$T$ \edge[draw=none]; $Q)$ ] ]
\edge[draw=none]; $\vee$ [ [.$F$ \edge[draw=none]; $R$ ] ] ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; $\leftrightarrow$ ]
[.$F$ [.$T$ [.$\sim F$ \edge[draw=none]; $(\sim R$ ] ]
\edge[draw=none]; [.\mbox{ } \edge[draw=none]; [.\mbox{ }
\edge[draw=none]; $\wedge$ ] ] [.$F$ [.$\sim T$ \edge[draw=none]; $\sim Q)$ ] ] ]
]
}
\end{tikzpicture}
\end{frame}
\end{document}
