Synthesis issues are driven mainly by repetitive structures, extreme GC content, and homopolymers. We use a machine learning method to determine the chance of success. Therefore, most of the time, there is no single reason for the rejection of a sequence. Rather, complexity or rejection stem from a combination of features that push a sequence into a given bucket of complexity. The only hard rules are the following:

• Avoid homopolymers >= 14bp

• Do not include CcdB (Type II Toxin-antitoxin system)

Should you encounter an issue, we recommend removing or minimizing repeats, regions of extreme GC content, and homopolymers. We will highlight regions of concern if your sequence is complex, unbuildable, or contains sequences which conflict with our internal processes.