new_contents: # Copyright (c) 2016 Kirill 'Kolyat' Kiselnikov
  # This file is the part of chainsyn, released under modified MIT license
  # See the file LICENSE.txt included in this distribution
  """
  Main module of chainsyn
  """
  
  from os import system
  
  from processing import replication
  from processing import transcription
  from processing import translation
  from processing import rev_transcription
  
  menu_items = ('1', '2', '0')
  item = ''
  
  m = True
  while m:
      try:
          system('clear')
      except OSError:
          system('cls')
      print()
      print('========')
      print('chainsyn')
      print('========')
      print()
      print()
      print('Main menu')
      print()
      print(menu_items[0], ' - Eucariotic cell polypeptide synthesis')
      print(menu_items[1], ' - Imitate full virus cycle')
      print(menu_items[2], ' - Exit')
      print()
      item = input('Choose menu item: ')
      if item not in menu_items:
          input('Please enter correct number of menu item')
      else:
          m = False
  
  if item == menu_items[0]:
      print()
      print('Enter source DNA chain with nucleotides A, T, C or G')
      dna1 = input()
      dna2 = replication(dna1)
      mrna = transcription(dna2)
      polypeptide = translation(mrna)
      # output
  if item == menu_items[1]:
      print()
      print('Enter virus mRNA chain with nucleotides A, U, C or G')
      mrna1 = input()
      dna1 = rev_transcription(mrna1)
      dna2 = replication(dna1)
      mrna2 = transcription(dna2)
      polypeptide = translation(mrna2)
      # output
  
  exit(0)
  
subject: Add sketch of main module 'start.py'