Custom DNA synthesis covers three different products that happen to share a chemistry: chemically synthesised oligos for primers and probes, linear double-stranded gene fragments assembled from oligos for cloning and assembly, and full-length genes synthesised, cloned into a vector and sequence-verified. Each is priced per base on a different scale and each solves a different problem. This page explains which to order for which job and how to read the vendor prices, then points at the comparison.
Oligos: short, fast and cheap per base
Oligos are single-stranded and made directly by phosphoramidite chemistry. They are the right product up to a length where full-length yield falls away, and they cover primers, probes, guides, short adapters and the building blocks of assembly. Price is per base by scale and purification, and for most laboratory work desalted material at the smallest scale is all that is needed. The oligo pages on this site record what each vendor publishes for that product.
Gene fragments: double-stranded, unverified, ready to assemble
A gene fragment is a linear double-stranded DNA assembled from overlapping oligos and delivered without cloning, sometimes without sequence verification of every molecule. It is the cheapest way to get a few hundred to a few thousand bases into a Gibson or Golden Gate assembly, and its weakness is that a fraction of molecules carry errors, so the assembled clone must be sequenced. Fragments are priced per base with a length cap and sometimes a complexity surcharge for repeats or extreme GC content.
Cloned genes: verified in a vector
A synthetic gene is assembled, cloned, sequence-verified across its full length and delivered as a plasmid, often with a glycerol stock. The per-base price is higher than a fragment because the cloning and verification are included, and the lead time is longer. For a coding sequence that will be expressed, codon optimisation is usually offered without charge and is worth using. This is the product to order when a wrong base cannot be tolerated and the construct will be reused.
Reading the vendor comparison
Vendors publish per-base prices for genes and fragments with length tiers and complexity rules, and the headline price is nearly always the simplest tier. The gene synthesis pages on this site record those published figures, verified on the vendor's own page and dated, so the like-for-like comparison at your length and complexity is visible before you request a quote. Send the actual sequence for a feasibility check, since complexity is judged differently by each vendor.
Questions people ask about custom dna synthesis
What is the difference between a gene fragment and a synthetic gene?
A fragment is a linear double-stranded DNA delivered without cloning and with a small error rate per molecule; a synthetic gene is cloned into a vector and sequence-verified across its full length.
How is custom DNA synthesis priced?
Per base, with different per-base rates for oligos, fragments and cloned genes, plus surcharges for complexity, modifications, purification and cloning into a customer vector.
How long does custom DNA synthesis take?
Oligos in days, fragments in about a week or two, cloned genes in a few weeks depending on length and complexity; each vendor states lead times by tier.
Should I codon optimise a synthetic gene?
For a sequence to be expressed in a heterologous host, yes; most vendors offer the optimisation as part of the order and it also removes many synthesis complexity problems.