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During the past year the results of deep sea drilling and other geophysical investigations have continued to strengthen the concepts of sea floor spreading and plate tectonics. Samples of lunar rock, too, have focused attention again on the history of the Earth.
The highlights of a year when microorganisms have proved more productive than ever for studying the genetic apparatus of cells have been the isolation and synthesis of DNA genes and the sequencing of RNA phage genes. First steps have been taken towards characterizing the enzymes which synthesize DNA and degrade RNA in bacterial cells. Protein synthesis in mammals is initiated in a way similar to bacteria; this supports the idea that the mechanisms of heredity are universal even in their details. A breakthrough in understanding the action of RNA tumour viruses has been the finding that they reverse the central dogma of molecular biology by directing synthesis of DNA.