From a monastery garden to programmable molecules — how four bases (A, T, G, C) became the operating system of life.
In an Augustinian monastery in Brno, Gregor Mendel cross-bred 28,000 pea plants and discovered that traits were inherited as discrete particles — not blended liquids.
A monk's data table that, decades later, would name a science.
April 1953, Nature: Watson & Crick publish a one-page paper proposing DNA's antiparallel double helix — built on Rosalind Franklin's X-ray crystallography (Photo 51).
Crick's 1958 "central dogma": genetic information flows in one direction. DNA stores it, RNA transports it, ribosomes translate it into the molecular machines (proteins) that do the work.
DNA → DNA. Polymerases unzip the helix and copy each strand semi-conservatively before cell division.
DNA → mRNA. RNA polymerase reads a gene; thymine (T) becomes uracil (U).
mRNA → protein. Ribosomes read codons (3 bases) and chain amino acids into a folded protein.
Three-letter words spell every protein in every species. The code is redundant (multiple codons per amino acid) and nearly universal — bacteria, ferns, and humans share it.
Excerpt — 32 of 64 codons shown.
Thirteen years, 20 institutions, $2.7 billion. Completed in 2003 — a complete reference of human DNA. The biggest surprise wasn't what it contained, but how little.
For comparison: a rice plant has ~32,000 protein-coding genes. Complexity isn't about gene count — it's about regulation.
For decades, the 98% of DNA that didn't code for proteins was dismissed as junk. The ENCODE project (2012) and successors have rewritten that story.
Copy-machine errors in DNA replication generate the raw material for evolution — and most disease. Three flavors:
One base swapped for another. Sickle cell: a single A→T changes one amino acid in hemoglobin.
Insertion or deletion shifts the reading frame — every codon downstream changes. Often catastrophic.
Whole sections duplicated or deleted. Down syndrome: a third copy of chromosome 21.
Driving on Highway 128 in 1983, Kary Mullis sketched a chain reaction that would double DNA every cycle. Thirty cycles → a billion copies of any chosen sequence.
Three generations of technology compressed the cost of a human genome from billions to hundreds of dollars in two decades.
Borrowed from a bacterial immune system: a guide RNA escorts the Cas9 enzyme to a precise location in the genome, where it cuts. Cellular repair finishes the edit.
Editing went from cutting (CRISPR) to rewriting (base editing) to drafting (prime editing). Genetic medicine is moving from theory to clinic.
One-time treatments for hemophilia, retinal blindness, spinal muscular atrophy. AAV viral vectors deliver corrected genes directly to target cells.
Rewrite single letters without cutting both strands. Prime editing (Liu, 2019) handles ~89% of known disease-causing mutations.
Pharmacogenomics tailors drugs to your variants. mRNA vaccines designed in days. Cancer immunotherapies engineered patient by patient.
23andMe-class consumer kits, ancient DNA from 400,000-year-old bones, the rewriting of human prehistory through genomes.
Designing organisms from scratch. Minimal genomes (Mycoplasma JCVI-syn3.0). Engineered yeast that brews insulin, spider silk, vaccine adjuvants.
Germline editing ethics. Off-target effects. Equity of access. What does it mean to "fix" a genome?
// FIN — A · T · G · C