Phoebus Leven (1869-1910)

Levene's Tetranucleotide Hypothesis

    Following establishment that nucleic acids were localized in the chromosomes, early experiments suggested that the four base molecules A C G T occur in approximately equal ratios.The Russian-American biochemist Phoebus Levene (1869-1940), who had discovered ribose sugar in 1909 and  deoxyribose sugar in 1929, suggested the structure of nucleic acid as a repeating tetramer. He called the phosphate - sugar - base unit  a nucleotide. The simplicity of this structure implied that nucleic acids were too uniform to contribute to complex genetic variation. Attention thereafter focused on protein as the probable hereditary substance.

    Note that in the tetranucleotide model, adjacent sugar molecules are connected by a 3'-5' phospho-diester linkage, just as in the Watson-Crick model. However, each four-nucleotide component is a separate molecule, and the bases are directed to the outside.

All text material ©2015 by Steven M. Carr