在乳胶图中绘制双向箭头

Question

我想在乳胶中重现下图：

我知道如何制作单向箭头，但我想将每对单向箭头表示为一个双向箭头。我想知道这里有没有人可以给我一些提示！

Answer 1

一个非常简单的尝试tikz-cd，但我不知道如何定义单个双向箭头。

\documentclass{article}
\usepackage{tikz-cd}

\begin{document}

\begin{tikzcd}[row sep=50, column sep=50, arrows={rightharpoondown, shift right=.25ex}]
    A \arrow[r] \arrow[d, "\beta"'] \arrow[dr, "\alpha"' pos=2/5] 
  & C \arrow[l, "\beta"'] \arrow[d] \arrow[dl] \\
    T \arrow[r, "\beta"'] \arrow[u] \arrow[ur] 
  & G \arrow[l] \arrow[u, "\beta"'] \arrow[ul, "\alpha"' pos=2/5]
\end{tikzcd}

\end{document} 

Answer 2

纯tikz：

\documentclass[12pt, tikz, margin=3mm]{standalone}
\usetikzlibrary{arrows.meta, positioning, quotes}

\begin{document}
    \begin{tikzpicture}[auto=right,
node distance = 32mm and 32mm,
 N/.style = {minimumsize=8mm},
ys/.style = {yshift=#1},
xs/.style = {xshift=#1}
                        ]
\node (a)                   {A};
\node (c)   [right=of a]    {C};
\node (t)   [below=of a]    {T};
\node (g)   [below=of c]    {G};
\draw[-{Straight Barb[right]}]
    ([ys= 1.4pt] c.west)  edge ["$\beta$"]    ([ys= 1.4pt] a.east)
    ([ys=-1.4pt] a.east)  edge                ([ys=-1.4pt] c.west)
    ([ys= 1.4pt] g.west)  edge                ([ys= 1.4pt] t.east)
    ([ys=-1.4pt] t.east)  edge ["$\beta$"]    ([ys=-1.4pt] g.west)
    ;
\draw[-{Straight Barb[left]}]
    ([xs=-1.4pt] t.north)   edge ["$\beta$" ']  ([xs=-1.4pt] a.south)
    ([xs= 1.4pt] a.south)   edge              ([xs= 1.4pt] t.north)
    ([xs= 1.4pt] c.south)   edge ["$\beta$" ']  ([xs= 1.4pt] g.north)
    ([xs=-1.4pt] g.north)   to                ([xs=-1.4pt] c.south)
%
    ([ys=-2pt] g.north west)  edge [pos=0.55,"$\alpha$" ']  ([xs=-2pt] a.south east)
    ([ys= 2pt] a.south east)  edge                          ([xs= 2pt] g.north west)
%
    ([xs=-2pt] t.north east)  edge [pos=0.55,"$\alpha$"]  ([ys= 2pt] c.south west)
    ([xs= 2pt] c.south west)   to                           ([ys=-2pt] t.north east)
        ;
\end{tikzpicture}
\end{document}