In the early 1970s, the field of genetics stood at a crucial threshold. While scientists understood that DNA encoded the information of life, no one had yet uncovered the full sequence of a gene. The question was not just what genes do—but how to read them. That breakthrough came in 1977, when Frederick Sanger achieved what had never been done before: the complete sequencing of a genome.

The organism chosen was not a complex one, but it was ideal—bacteriophage ΦX174, a small virus that infects bacteria. Its genome consisted of just 5,386 nucleotides, making it a manageable candidate for what was still an uncharted experimental journey.

Sanger employed a novel technique now famously known as Sanger sequencing, or dideoxy chain termination sequencing. At the heart of the method was a clever idea: by incorporating chemically modified nucleotides (dideoxynucleotides) that terminate DNA synthesis at specific bases, Sanger generated DNA fragments of varying lengths. When these fragments were run through a gel, the sequence could be read—one nucleotide at a time—by determining where synthesis had stopped.

It was labor-intensive, precise, and required immense manual effort. But it worked. In sequencing the ΦX174 genome, Sanger produced the first ever fully sequenced DNA genome, launching a revolution that transformed molecular biology, biotechnology, and medicine.

Why does this matter today?

This achievement laid the groundwork for:

The Human Genome Project, completed in 2003, which revealed the full sequence of our own genetic code

The rise of personalized medicine, where genetic information guides individual treatment strategies

Advances in synthetic biology and bioengineering, which depend on the ability to read and write genetic information

The development of next-generation sequencing technologies that can analyze entire genomes in hours

Today’s innovations—from CRISPR to AI-driven diagnostics—trace their origins to the first successful sequencing of a gene. The ability to decode life at the molecular level began with this one experiment.

What began with a bacteriophage and a handful of radioactive reactions now drives billion-dollar biotech industries, shapes public health responses, and fuels scientific discovery across the globe.