In the present day, information about DNA (deoxyribonucleic acid) is just about everywhere. Using recombinant DNA to make therapeutically important proteins, DNA fingerprinting in forensic science, information concerning the genetic code, attempts undertaken at gene therapy, all seems to be part of the popular lexicon. Most of this information is based on discoveries of the last 30 to 50 years, yet DNA was first discovered in the 19th century.
Components of the Cell
During the 1800s, as the compound microscope improved, scientists became more and more interested in the structures that they could now visualize inside of the cell. This ultimately progressed to the description of the cell theory of biology by Schleiden and Schwann in the late 1830s. This theory stated that all organisms are made up of their component cells, the cells being the simplest, sustainable structural unit.
Most early discoveries about cellular structure came from the study of plant cells. It was the description of the nucleus by Robert Brown in the 1830s that led many other scientists of the day to examine cellular structure in animal cells. It is these types of studies that led to the cell theory.
The Discovery of Nuclein
After being educated as a physician in his native Switzerland, Johann Friedrich Miescher (1844-1895), made an important decision; because of his poor hearing he would not pursue a strictly clinical medical career, but rather would become involved in research. Leaving Switzerland, he moved to Germany to join the laboratory of the famous physician and physiological chemist, Ernst Felix Hoppe-Seyler, who had already achieved great renown with his work on blood cells and hemoglobin.
At this time, antibiotics did not exist in medical practice, and consequently, wounds routinely became infected. One of the major cellular constituents of the pus in infected wounds is white blood cells. Recognizing that the white blood cells had a nucleus, Miescher set out to collect large numbers of them by washing them out of the bandages used to wrap patient’s wounds.
Using various extraction methods that were routinely used at that time, Miescher isolated nuclei from the white blood cells and then an unknown substance from the collected nuclei. He knew that it was not protein based on what was then known about the chemical behavior of proteins. He also recognized from his tests that it had peculiar solubilities and contained very large amounts of phosphorus. In 1869 he reported to Dr. Hoppe-Seyler his isolation and characterization of a compound he referred to as “nuclein”.
A short time later, Miescher returned to Switzerland and continued performing research, isolating nuclein from a number of different sources. It was not until a few years after his discovery that this substance came to be called nucleic acid. And of course it was not until well into the next century that this nucleic acid became known as the molecule responsible for the inheritance of traits from one generation to the next. It would be almost 100 years after Miescher’s initial discovery, that the genetic code for inheritance contained in this molecule he called nuclein was cracked.
Read more about Miescher in this informative article written by Dr. George Wolf and posted on the Miescher family website.
Additional Source:The Eighth Day of Creation: Makers of the Revolution in Biology by Horace F. Judson, expanded edition 1996, Cold Spring Harbor Laboratory, ISBN: 0879694785
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