copySeq = T.map copyNt . toDna
  where 
    copyNt nt = case nt of 
      'A' -> 'A'
      'T' -> 'T' 
      'G' -> 'G' 
      'C' -> 'C'
      _   -> 'N'
copySeq = T.map copyNt . toDna
  where 
    copyNt nt = case nt of 
      'A' -> 'A'
      'T' -> 'T' 
      'G' -> 'G' 
      'C' -> 'C'
      _   -> 'N'
copySeq = T.map copyNt . toDna
  where 
    copyNt nt = case nt of 
      'A' -> 'A'
      'T' -> 'T' 
      'G' -> 'G' 
      'C' -> 'C'
      _   -> 'N'