Genome Synthesis

Every living being carries a set of building instructions in its cells. They are stored in a long molecule called DNA, which consists of a chain of four recurring building blocks. The order of these building blocks is the actual text of the instructions, and the totality of these instructions is called the genome. In genome synthesis, such a genome is rebuilt from scratch in the lab, building block by building block. The template used is not a real cell, but a file on a computer. You can think of it like a printer: a text file goes in at the top, and a tangible molecule comes out at the bottom.

From reading to writing genetic material

For decades, biology could only read genetic material. DNA was extracted from a cell and the order of its building blocks was determined. This is called sequencing. Genome synthesis is the reverse path: writing instead of reading. This turns biology into a technology that can be designed on a screen.

This opens up possibilities that cannot be achieved through classical breeding. Researchers can modify bacteria so that they produce medicines or plastics. They can also deliberately simplify genetic material to understand which parts an organism truly needs to live. A well-known project is the reconstruction of the yeast genome by an international consortium. Yeast is a fungus known from baking, and its genetic material is more similar to that of animals and humans than to that of bacteria.

At the same time, the technology is sensitive. Anyone who can freely write genetic material could, in principle, also recreate the genetic material of dangerous viruses. That is why commercial providers check incoming orders for suspicious sequences. This check is called biosecurity screening and has become a political controversy in its own right.

From building block to chromosome

Chemistry cannot produce DNA of arbitrary length all at once. At around two hundred building blocks, errors accumulate too much. That is why the process happens in stages. First, many short pieces, so-called oligonucleotides, are created, often in parallel on a small chip.

These short pieces are then joined into longer segments. The ends are designed so that they only fit with the correct neighbor, similar to puzzle pieces. This first produces segments of a few thousand building blocks, then of hundreds of thousands. For the final, largest steps, living cells are often used as a workshop, because yeast joins foreign DNA pieces together very reliably.

In the end, the finished genome must be introduced into a cell whose own genetic material has been removed. Only when the cell grows and divides with it is the synthesis considered successful. Every intermediate step is sequenced, that is, read, to find errors. A single incorrect building block can render an important gene unusable. Genome synthesis is therefore less a single process than a long chain of building and checking.

Why this appears in tech news

Genome synthesis is usually mentioned in connection with synthetic biology. This refers to the approach of constructing living organisms like technical systems. Companies in this field sell custom-made DNA, often as an order placed via a website. The price per building block has fallen sharply over the years, similar to memory chips.

For some years now, AI has entered the picture. Programs can suggest what a DNA sequence would need to look like for a protein to perform a desired task. These suggestions are initially just text in a file. Only genome synthesis turns them into something that can be tested in the lab. It is precisely this combination that explains why the topic also appears on business pages.

A common misconception is that genome synthesis is the same as gene-editing methods like CRISPR. A gene editor changes individual spots in an existing genome, much like correcting a word in a text. Genome synthesis rewrites the text from the very beginning. The two are often combined, but are technically clearly distinct.