\documentclass[tikz,border=10pt]{standalone}
\usepackage{amsmath}
\definecolor{bg}{HTML}{171D2B}
\definecolor{acc}{HTML}{F7B538}
\begin{document}
\pagecolor{bg}
\begin{tikzpicture}[
  line/.style={draw=white, thick},
  lab/.style={text=acc, font=\small},
  res/.style={text=white, font=\small},
  level distance = 30mm,
  level 1/.style = {sibling distance = 46mm},
  level 2/.style = {sibling distance = 23mm},
  grow = right
]
  \node[res] {Awal}
    child { node[res] {A}
      child { node[res] {AA} edge from parent[line] node[lab,below] {$\tfrac12$} }
      child { node[res] {AG} edge from parent[line] node[lab,above] {$\tfrac12$} }
      edge from parent[line] node[lab,below] {$\tfrac12$}
    }
    child { node[res] {G}
      child { node[res] {GA} edge from parent[line] node[lab,below] {$\tfrac12$} }
      child { node[res] {GG} edge from parent[line] node[lab,above] {$\tfrac12$} }
      edge from parent[line] node[lab,above] {$\tfrac12$}
    };
\end{tikzpicture}
\end{document}