The Avery–MacLeod–McCarty experiment<span> was an experimental demonstration, reported in 1944 by </span>Oswald Avery<span>, </span>Colin MacLeod<span>, and </span>Maclyn McCarty<span>, that </span>DNA<span> is the substance that causes </span>bacterial transformation<span>, in an era when it had been widely believed that it was </span>proteins<span> that served the function of carrying genetic information (with the very word </span>protein<span> itself coined to indicate a belief that its function was </span>primary<span>).
It was the culmination of research in the 1930s and early 20th Century at the </span>Rockefeller Institute for Medical Research<span> to purify and characterize the "transforming principle" responsible for the transformation phenomenon first described in </span>Griffith's experiment<span> of 1928: killed </span>Streptococcus pneumoniae<span> of the </span>virulent<span> strain type III-S, when injected along with living but non-virulent type II-R pneumococci, resulted in a deadly infection of type III-S pneumococci.
In their paper "</span>Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III<span>", published in the February 1944 issue of the </span>Journal of Experimental Medicine<span>, Avery and his colleagues suggest that DNA, rather than protein as widely believed at the time, may be the hereditary material of bacteria, and could be analogous to </span>genes<span> and/or </span>viruses<span> in higher organisms.</span>
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The magnetic field is generated by electric currents due to the motion of convection currents of molten iron in the Earth's outer core: these convection currents are caused by heat escaping from the core, a natural process called a geodynamo.
