title: Python structure mistake
body: <p>I'm writing a program in which I can Reverse the sequence and Replace all As with Ts, all Cs with Gs, all Gs with Cs, and all Ts with As. the program is to read a sequence of bases and output the reverse complement sequence. I am having trouble to do it so can anyone please help me with this by having a look on my code:</p>
  
  <pre><code>word = raw_input("Enter sequence: ")
  a = word.replace('A', 'T')
  b = word.replace('C', 'G')
  c = word.replace('G', 'C')
  d = word.replace('T', 'A')
  if a == word and b == word and c == word and d == word:
      print "Reverse complement sequence: ", word
  </code></pre>
  
  <p>And I want this sort of output:</p>
  
  <pre><code>Enter sequence: CGGTGATGCAAGG
  Reverse complement sequence: CCTTGCATCACCG
  </code></pre>
  
  <p>Regards</p>