Early Method Packages Recombinant DNA Directly Into Phage Particles

Hohn and Murray, writing in the Proceedings of the National Academy of Sciences in 1977, describe a laboratory method for building recombinant DNA molecules and immediately packaging them into bacteriophage particles — virus shells that infect bacteria — without needing to grow the DNA inside living cells first.

This is a molecular biology and enzymology study, done entirely with purified enzymes and viral components in a test tube (in vitro), not in animals or humans. The researchers joined DNA fragments using a ligase enzyme, formally called poly(deoxyribonucleotide):poly(deoxyribonucleotide) ligase, which stitches DNA strands together. They report that the packaging process worked efficiently and did not favor one type of DNA molecule over another, and that it offered a way to contain recombinant DNA safely during the early handling steps — a real concern in genetic engineering research at the time. One technical complication: the ligase-joined DNA could sometimes combine with the phage's own natural DNA during packaging, but the authors found that UV irradiation could destroy the biological activity of that natural DNA, cleaning up the results.

The abstract gives no further numeric detail on yields or efficiency percentages, and as a pure methods paper, it says nothing about biological or therapeutic effects of DNA fragments.