Experiment #70 · Scientific experiment

The Hershey–Chase Experiment

DNA is the genetic material

Alfred Hershey and Martha Chase · 1952 · Molecular biology

First published: A. D. Hershey & M. Chase, "Independent functions of viral protein and nucleic acid in growth of bacteriophage", *Journal of General Physiology* 36 (1952): 39–56.

Bacteriophage protein tagged with sulphur-35, DNA tagged with phosphorus-32. Only the phosphorus enters infected bacteria. DNA is the genetic material.

Hershey and Chase used bacteriophages (viruses that infect bacteria) whose protein coats and DNA cores were separately radiolabelled — protein with ³⁵S, DNA with ³²P. After infection, blender agitation sheared off the empty viral coats, and centrifugation separated bacteria from coats. The bacteria contained the phosphorus (DNA) but very little sulphur (protein); the next phage generation also carried the phosphorus. Conclusion: DNA, not protein, is what enters the cell and directs the production of new virus — DNA is the genetic material. Combined with the Avery-MacLeod-McCarty experiments and preparing the way for Watson-Crick (1953), the result was the empirical foundation of molecular genetics.

Formulation

Phage T2 grown in ³⁵S (labels protein) or ³²P (labels DNA) → infect E. coli → blender shear → centrifuge separates cells from coats. ³⁵S: in supernatant (coats outside). ³²P: in pellet (DNA inside cells). Conclusion: DNA enters; protein doesn't; DNA carries heritable information.

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Dimensions Engaged

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Matter

Identifies the physical bearer of biological inheritance with a specific molecular structure: DNA.

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Information

Foundational for biological Information · Ontological Status: the genetic information has a specific material implementation that can be tracked and manipulated.

Responses — How Schools Engage

Affirms / takes the bait 5

Naturalism

A canonical empirical result that opened molecular biology: the abstract gene of Mendelian genetics now has a chemical identity.

Realism

DNA is the real bearer of heredity. Scientific realism vindicated at the molecular level.

Structuralism

DNA is identified by its structural role: a polymer encoding sequence information, distinguished from protein by both function and physical persistence through infection.

Dataism / Information Ontology

The discovery that heredity is implemented as sequence information in a specific molecule is foundational for the information ontology of biology.

Analytic Metaphysics / Logical Atomism

Hershey-Chase plus Watson-Crick (1953) demonstrate that biological information reduces to chemical sequence; reductive naturalism (the analytic-metaphysics inheritance of Quinean reductionism) is empirically supported at the cellular level.

Reframes the question 1

Process Philosophy

DNA is real but is not the whole story: gene expression, regulation, and epigenetic inheritance are processual phenomena that pure DNA-centrism overlooks.