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Components of Cells
The Macromolecules
Discovery of DNA
A source of the material

Friedrich Miescher
In 1865, the year that Gregor Mendel ("Brother Gregory" in these stories) published his paper on the hybridization of plants, and thus started the science of heredity and genetics, the University of Tubingen took a bold educational step and became the first Germany University to start a department of "natural science".

Three years later (1868) Felix Hoppe-Seyler, a leader in this new field of tissue chemistry at Tubingen, took on a new researcher - one Friedrich Miescher - a up and coming young dynamo who had an already established research reputation.

Miescher, in his own words "was fascinated by the thought of tracing the most generally valid conditions of cell life from the simplest and independent forms of animal cells".

Source of the DNA
One source of these "independent animal cells" was the discarded bandages from surgical wards of hospitals. In days before antibiotics, wounds oozed yellow pus cells, as the damaged flesh healed. These pus cells were absorbed by the bandages, and Miescher could wash them out, and collect reasonable numbers, with relatively little effort.

When either whole pus cells, or later, when pure nuclei were treated with weakly alkaline solutions followed by acid neutralization, a precipitate was obtained which "cannot belong among any of the protein substances known hitherto". Miescher was the first person to see DNA!

At first this substance was called nuclein, was found in cells from yeast, kidney, liver, and nucleated blood cells, and had none of the classic properties of proteins; what was it?

As well as containing the elements hydrogen, carbon, nitrogen and oxygen, Miescher also found phosphorus and that the ratio of phosphorus and nitrogen in this substance was unique. So Miescher thought that his "nuclein" was nothing more than a storehouse of phosphorus waiting to be used by the cells for more interesting purposes!

His boss, Hoppe-Seyler was so unimpressed that he delayed publishing these discoveries and the war of 1870 further delayed matters. After checking Miescher's results, and extending the discovery of nuclein to other substances, a paper announcing it's discovery was finally published in 1871. But no one understood what this material was or what it did.

Those discoveries were to take a lot longer.

Figure legend: Pus cells from the bandages of bleeding patients were an important first source of "independent animal cells". Later, the material called nuclein was found in lots of other animal and plant material, but it was some time before the difference between DNA and RNA were fully described.

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© 2001, Professor John Blamire