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    How DNA synthesis and assembly work

    DNA synthesis turns a digital sequence into physical DNA: short strands are made chemically or enzymatically, then assembled into genes, pathways and whole chromosomes.[1][2] Length and error rate are the binding constraints, which is why writing a bacterial genome still means synthesising dozens of fragments and debugging the result.[3][4]

    Editor reviewedUpdated Synthetic biologyLife sciencesScience

    Why writing DNA is the starting point

    Every other step in synthetic biology depends on getting a designed sequence into a molecule. Gene-length DNA is now an industrial product: Twist Bioscience alone shipped about 369,000 genes in the three months to June 2026, up from about 237,000 a year earlier.[5]

    Think of DNA synthesis as printing. A machine adds one chemical letter at a time to a growing strand, building short pieces called oligonucleotides. Those short pieces are then joined into genes, and genes into longer stretches such as a metabolic pathway or a chromosome.[1][2]

    The catch is accuracy. Each added letter has a small chance of going wrong, so the longer the strand the more likely it carries a mistake. That is why long DNA is made from many short pieces that are checked, assembled and then grown inside cells, which copy the correct version faithfully.[6][4]

    Two chemistries compete. Phosphoramidite synthesis is the long-established route and underpins most array-based gene production. Enzymatic synthesis instead uses a template-independent polymerase to extend a strand in aqueous conditions, which vendors argue reduces strand damage and so extends usable length; Ansa Biotechnologies markets clonal constructs up to 50 kb on an enzymatic platform and says conventional approaches generally cannot exceed about 10 kb.[6][2] Those are vendor claims and should be read as such.

    Price and turnaround are the practical design constraints: about 28 cents per base pair and under 25 business days for long clonal DNA in late 2025.[7] For benchtop work, DNA Script’s SYNTAX prints oligonucleotides on site in hours rather than shipping them.[1]

    From oligos to genomes

    Assembly is a hierarchy. Short synthetic fragments are joined into genes, genes into cassettes, and cassettes into chromosome-scale sequences, usually by homologous recombination in yeast or by recombinase-mediated replacement in the target organism.[3] The Sc2.0 project applied that hierarchy across the whole yeast genome, finishing with the 903-kilobase synthetic chromosome synXVI in January 2025.[8]

    Recoding shows how far the approach now reaches. Syn57, an Escherichia coli strain reported in Science in 2025, has a four-megabase synthetic genome carrying more than 101,000 codon changes, which removed seven codons from its genetic code.[3][9]

    Debugging is part of the method

    A synthesised genome is a design hypothesis, and designs fail. The Sc2.0 teams used a CRISPR-based protocol, D-BUGS, to localise the specific design changes that impaired growth and then correct them.[4] Projects therefore budget for iteration: build, measure, find the broken region, redesign.

    What to watch

    Capacity and decentralisation are both moving. DNA Script extended distribution of on-demand synthesis to Latin America and East Asia in March 2026 and to India in July 2026, and in August 2026 it said it and GE HealthCare had been awarded up to $26 million by ARPA-H for cell-free DNA bioproduction.[10][11] Meanwhile the economics of gene synthesis keep improving: Twist’s DNA synthesis and protein unit grew to $56.6 million in the quarter to June 2026 from $40.8 million a year earlier.[12]

    Because synthesis is also the point at which a sequence of concern could enter a laboratory, order screening sits directly on top of this supply chain; see dna-synthesis-screening.[13]

    Questions readers ask

    How long a piece of DNA can be made today?

    Commercial clonal DNA reaches about 50 kilobases from enzymatic providers; Ansa Biotechnologies says conventional approaches generally stop short of about 10 kilobases.[6][2]

    What does synthetic DNA cost?

    Long clonal constructs were advertised from about 28 cents per base pair in late 2025, with turnaround under 25 business days.[7]

    How is a whole genome written if fragments are short?

    It is built in pieces. The Syn57 Escherichia coli genome was synthesised as fragments and recombined, and its four-megabase sequence carries more than 101,000 codon changes.[3]

    Do synthetic genomes work first time?

    Usually not. The synthetic yeast project used a CRISPR-based debugging protocol to find and fix design errors that slowed growth.[4]

    Sources

    Each numbered claim is a statement we checked against the sources listed with it. Status shows how well established it is.

    1. [1]

      DNA Script's SYNTAX system is a benchtop enzymatic DNA printer that produces custom oligonucleotides on site in hours rather than days. reportedas of 2026-10-10

    2. [2]

      Ansa Biotechnologies says industry-standard DNA synthesis approaches generally cannot produce constructs longer than about 10 kilobases. reportedas of 2025-10-01

    3. [3]

      Syn57 is an Escherichia coli strain whose 4-megabase genome was built by total synthesis with more than 101,000 codon changes, giving it a 57-codon genetic code; the work was published in Science in 2025. confirmedas of 2025-08-01

    4. [4]

      The Sc2.0 team used a CRISPR-based debugging protocol, D-BUGS, to locate and correct design errors in synthetic chromosomes that impaired yeast growth. confirmedas of 2025-01-22

    5. [5]

      Twist Bioscience shipped about 369,000 synthetic genes in the third quarter of fiscal 2026, against about 237,000 in the same quarter of fiscal 2025. confirmedas of 2026-08-05

    6. [6]

      Ansa Biotechnologies announced commercial availability of clonal DNA constructs up to 50 kilobases made on its enzymatic DNA synthesis platform, roughly 100 times longer than its first product. reportedas of 2025-10-01

    7. [7]

      Ansa Biotechnologies listed its long clonal DNA from as little as 28 cents per base pair with turnaround under 25 business days. reportedas of 2025-10-01

    8. [8]

      The final synthetic chromosome of the Sc2.0 project, the 903-kilobase synXVI, was reported in Nature Communications on 20 January 2025. confirmedas of 2025-01-22

    9. [9]

      Syn57 removes seven codons from the genetic code: four that encode serine, two that encode alanine and one stop codon. confirmedas of 2025-08-01

    10. [10]

      DNA Script expanded distribution of on-demand DNA synthesis to Latin America and East Asia in March 2026 and to India in July 2026. confirmedas of 2026-07-16

    11. [11]

      On 4 August 2026 DNA Script said it and GE HealthCare had been awarded up to $26 million by ARPA-H to advance cell-free DNA bioproduction under the FLASH programme. confirmedas of 2026-08-04

    12. [12]

      Twist Bioscience's DNA Synthesis and Protein Solutions revenue reached $56.6 million in the third quarter of fiscal 2026, up from $40.8 million a year earlier. confirmedas of 2026-08-05

    13. [13]

      The 2024 framework makes it a condition of US federal life-sciences research funding that synthetic nucleic acids, and benchtop devices that can make them, are bought only from providers and manufacturers that comply with the framework. confirmedas of 2026-10-10

    Revision history (2)
    1. Page created.
    2. Refresh: re-sourced the benchtop enzymatic synthesis description and the distribution claims to DNA Script press releases.

    Created Oct 10, 2026. Last reviewed by an editor on Oct 10, 2026. Next scheduled review: Jan 10, 2027.

    Cite this page

    "How DNA synthesis and assembly work." ContentLora, updated Oct 10, 2026. https://contentlora.com/explain/how-dna-synthesis-works

    Spotted an error? Suggest a correction or emailcorrections@contentlora.com.

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