Complex segments in the sequence make synthesis of oligo challenging and reduce the efficiency of transcription and translation. Complexities in a sequence include:

• Streches of direct or inverted repeats (>20 bp)
  
• homopolymeric streches (>18 bp)
  
• Streches of sequence that can result in critical secondary structures
• Streches of sequence with very high (>75%) or low (<35%) GC content.

Secondary structures reduce the synthetic yields of DNA oligos while also reducing the translational efficiency, since these secondary structures are then adopted by the mRNA. Any Genes or GeneStrands that contain these features are considered 'complex' and take longer to assemble.

These complexities can also be removed when GENEius is used to optimize the sequence. GENEius, which is integrated into the order wizard used for ordering Genes or GeneStrands, allows for seamlessly removing the complex features in a sequence. The use of GENEius is optional, and your sequence of choice can be assembled—please contact a sales representation for your region for inquiring about feasibility and potential turnaround times.