title: strsplit one column with exact information into two column
body: <p>I have data looking like this:</p>
  
  <pre><code>    SNP Geno Allele
  marker1   G1    AA
  marker2   G1    TT
  marker3   G1    TT
  marker1   G2    CC
  marker2   G2    AA
  marker3   G2    TT
  marker1   G3    GG
  marker2   G3    AA
  marker3   G3    TT
  </code></pre>
  
  <p>And I want it to look like this:</p>
  
  <pre><code>    SNP Geno Allele1 Allele2
  marker1   G1       A       A
  marker2   G1       T       T
  marker3   G1       T       T
  marker1   G2       C       C
  marker2   G2       A       A
  marker3   G2       T       T
  marker1   G3       G       G
  marker2   G3       A       A
  marker3   G3       T       T
  </code></pre>
  
  <p>I am using this:</p>
  
  <pre><code>strsplit(Allele, split extended = TRUE)
  </code></pre>
  
  <p>But this is not working. Do I need additional commands?</p>