A claimed new way life makes DNA
A widely shared post highlighted a Science.org story describing what researchers call a ‘fundamentally new way’ that life can produce DNA — a finding that surprised many readers and circulated heavily on X (x.com). The post linked readers to the report and sparked discussion about how the mechanism reshapes basic assumptions about molecular biology (x.com).
Life usually makes DNA by copying a nucleic-acid template. A Science paper published April 17, 2026 reported a bacterial enzyme that built a matching DNA strand without any DNA or RNA template. (science.org) DNA polymerases and reverse transcriptases are generally known as molecular copiers: they read an existing strand and add matching letters one by one. In the new study, a bacterial antiphage system called DRT3 made alternating poly(GT/AC) double-stranded DNA, and one of its two enzymes, Drt3b, made the poly(AC) strand by a protein-primed, protein-templated process. (science.org) The work came from researchers at Stanford University led by Alex Gao. Their cryo–electron microscopy structures, at 2.6 angstrom resolution, showed a 6:6:6 complex of Drt3a, Drt3b, and a noncoding RNA. (science.org) The noncoding RNA still matters, but not in the usual way for both strands. The paper said Drt3a uses a conserved ACACAC sequence in that RNA to make the poly(GT) strand, while Drt3b makes the complementary poly(AC) strand “in the complete absence of a nucleic acid template.” (science.org) That is narrower than “life makes DNA without templates” in general. The finding describes one antiphage reverse transcriptase in bacteria, not the main way cells copy their genomes. (science.org; genome.gov) The study fits a fast-growing corner of microbiology in which bacteria use reverse transcriptases as antiviral weapons. A 2025 Science paper on a related system, DRT9, found that it makes long poly(A)-rich complementary DNA, up to about 5,000 nucleotides, during phage defense after sensing changes tied to ribonucleotide reductase and deoxyadenosine triphosphate, or dATP. (science.org) That earlier DRT9 work already showed these enzymes can make unusual DNA products in defense systems. The 2026 DRT3 paper goes further by describing sequence-specific DNA synthesis directed by the protein itself, rather than by a nucleic-acid template. (science.org; science.org) The authors framed the result as an expansion of what nucleic-acid polymerases can do. They wrote that the finding “reveals a protein-templated mechanism for sequence-specific DNA synthesis,” placing it outside the two usual buckets of template-directed copying and simpler template-independent nucleotide addition. (science.org) The immediate biological role is bacterial self-defense, not human genetics or textbook DNA replication in plants and animals. The larger implication is that microbes carry more ways to build nucleic acids than biologists had mapped before April 2026. (science.org; science.org)
