FoundationalConceptsNeuroscience

tute in New York described experiments with pneumococcal bacteria
demonstrating that DNA can carry genetic information from one cell
to another. The work of Avery and colleagues was published in the
Journal of Experimental Medicine; their report concluded by stating
that “the evidence presented supports the belief that a nucleic acid
of the deoxyribose type is the fundamental unit of the transforming
principle.” However, their work failed to convince others interested
in the physical basis of heredity that genes were composed of DNA.
It’s not that Avery’s work was thought to be wrong or sloppy science.
It’s just that because DNA was too “stupid” a molecule to carry genetic
information—genes simply could not be made of DNA. Thus, Avery’s
work was essentially ignored. In addition, E. coli and bacteriophages
had become the system of choice for the mainstream researchers in
the field, and those researchers tended not to take too seriously work
conducted with other organisms.
Although Avery’s work was published in 1944 and essentially
ignored, after a few more years went by there was more willingness
to entertain the possibility that genes might be made of DNA. In
was only in 1952, however, that an experiment conducted by Alfred
Hershey (1908-1997) and Martha Chase (1927-2003) convinced
the scientific community that DNA, and not protein, was indeed the
carrier of genetic information. Hershey and Chase were members of
the mainstream community of bacteriophage researchers and used E.
coli bacteria and bacteriophages in their demonstration (Fig. 4.3). And
their experiment is one of great elegance and simplicity.
Hershey and Chase used a bacterial virus called phage T2. They
grew T2 on two different media: one containing radioactive sulfur
atoms and another containing radioactive phosphorus atoms. Two
of the twenty amino acids, cysteine and methionine, contain sulfur.
Thus, most proteins contain sulfur, whereas DNA does not contain