Figure 1

Assembly of Parts Using the BioBrick Standard Format. The promoter and the protein coding sequence, initially existing as parts on separate plasmids, are digested and ligated to form a composite part on one plasmid. Because XbaI (TCTAGA) and SpeI (ACTAGT) form compatible ends (CTAG), the two individual parts are connected by a mixed restriction site (ACTAGA) that is not recognized by any restriction endonuclease and is called the "scar". The individual parts may exist on plasmids with different resistances and the final composite parts may or may not be on a plasmid with the same resistance as its constituent parts.