ABSTRACT
First half of the twentieth-century as being the great age of physics, then the second half surely belongs to genetics. Genes were discussed endlessly in books, newspaper articles, and conversations, often by people who seemed only vaguely to understand what a gene is. In the 1900s, some researchers began to suspect that the genes could be located in the chromosomes, small thread-like bodies found in the nucleus of each living cell in every organism's body. Chromosomes were known to be made of protein and deoxyribonucleic acid (DNA), but people assumed that the genes were in the protein part. Further studies of this phenomenon showed that almost all of escherichia coli's genome is contained in one big loop of DNA, but there is sometimes another small loop, called a 'plasmid'. Especially in the late 1940s and 1950s, genetics was widely seen as the place to be, where the most exciting discoveries were waiting to be made.
