The past few years have seen the emergence of custom gene synthesis as a useful but expensive service available for molecular biologists. Recently, the number of companies offering custom gene synthesis has exploded, pushing the cost of the service down to much more affordable levels.

Custom gene synthesis derives from oligonucleotide synthesis technology, which has been used for years to used to make PCR primers. Oligos are synthesized in a automated chemical process in which the bases are joined in the desired order on a solid support. The inefficiency of this chemical process means that the oligo length is limited to a maximum of around 120 bases… that’s around 1/10th of the average gene length. Gene synthesis builds on this platform using proprietary technologies to join the oligos to make your full gene, and most companies will even clone the product into your desired vector for you

The immediate advantages of gene synthesis over conventional PCR are obvious and commonly cited. Since there is no need for template DNA previously unaccessible genes from hosts that are hazardous, hard to obtain or difficult to extract genomic DNA from can be now by accessed. Codon usage issues can also be overcome by designing the DNA sequence to include only the codons most commonly used in the intended expression host. Gene synthesis also brings a welcome predictability to the uncertain discipline of gene isolation and cloning.

An additional, but less mentioned, use of gene cloning is to change the DNA sequence to produce a modified protein product. As a customer, you can specify as many point mutations as you like in your gene sequence, and you could even make those mutations degenerate so that your synthesised gene becomes a library containing every possible amino acid at a given point in the protein. Alternatively, you could have the first few codons of a poorly expressed gene replaced by those of a well-expressed native gene, or add a tag to the N or C-terminal of the protein.

The lowest price I have seen for a synthesised, cloned gene is $0.69/base, which puts the purchase cost of a cloned 1kb gene at $690. This is still a little high to consider custom gene synthesis for routine cloning, but as the price drops further, cloning a gene will become just like ordering an oligo, accelerating the pace of our research even further.

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