DNA synthesis

DNA is the molecule in which living organisms store their construction plan. It consists of a long chain of four different building blocks, abbreviated with the letters A, C, G, and T. The order of these letters is the information – much like the order of characters in a text. DNA synthesis means: a machine in the lab artificially assembles this chain, letter by letter, following a template that was previously written on a computer. So nothing is taken from a living organism and copied; instead, something is newly manufactured. You can imagine it like a printer that, instead of ink on paper, links chemical building blocks together.

From text on a screen to a real molecule

The value of this technology lies in connecting two worlds. On a computer, a sequence of letters can be changed, copied, and sent around at will. But until a few decades ago, it was very difficult to turn such a file into an actual molecule. DNA synthesis closes exactly this gap.

This turns biology into a discipline where you can design before you experiment. A research team writes a gene sequence, orders it from a supplier, and receives it by mail a few days later. This was crucial for the COVID vaccine: the virus’s letter sequence was available online early on, and the first vaccine candidates were created in the lab without anyone needing the virus itself for it.

That is exactly why this technology is also a security issue. Anyone who can order a dangerous sequence bypasses the usual controls for biological material. Reputable suppliers therefore screen orders against lists of known pathogens. In many countries, this screening is not legally required but rather a voluntary industry commitment.

How the building blocks are linked together

The common method works in cycles. The first building block is attached to a solid support. Then the next building block is added and chemically coupled, excess material is washed away, and the cycle begins again. Each letter requires such a round.

Each step has a small error rate, and these errors add up. This is why only short pieces result from this process, usually fewer than 200 building blocks. Whole genes or genomes are assembled from many such short fragments, which are then joined together in an overlapping manner. For comparison: the human genome has around three billion building blocks – full synthesis is still far from that.

When it comes to the question of which sequence should even be produced, software comes into play. Programs from AI research predict what shape a protein arising from a particular sequence will take. Other models do the reverse, proposing sequences for a desired function. The design then comes from the computer, and synthesis delivers the molecule for testing.

Vaccines, enzymes, and data in a test tube

The technology is most visible in medicine. mRNA vaccines are based on synthetically produced genetic material, and many cancer therapies are also designed individually for a patient. In diagnostics, synthetic DNA pieces are found in almost every PCR test.

In industry, microorganisms are re-engineered so they produce certain substances. Insulin, enzymes for detergents, or flavorings are now often produced in bacteria or yeast that have had synthetic genes inserted into them. Another field is data storage: DNA can hold information extremely densely and for millennia, but it is far too slow to read and write for everyday applications.

In business news, this usually brings up company names like Twist Bioscience or Ginkgo Bioworks. The key metric there is the price per building block, which has fallen sharply over the years. A common misconception, by the way, is confusing DNA synthesis with gene-editing methods like CRISPR. CRISPR alters existing genetic material within a cell; synthesis, on the other hand, creates new material outside a cell in the first place.