Phoebus Leven (1869-1910)

Levene's Tetranucleotide Hypothesis (1910)

    Following establishment that nucleic acids were localized in the chromosomes, early experiments suggested that the four base molecules adenine, guanine, cytosine, and thymine occur in approximately equal ratios.The Russian-American biochemist Phoebus Levene (1869 - 1940), who had discovered ribose sugar in 1909 and went on to discover deoxyribose sugar in 1929, suggested that the structure of nucleic acid was 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 the other component of chromosomes, protein, as the probable hereditary substance.

    Note that in this model, adjacent sugar molecules are connected by a 3'-5' phospho-diester linkage and bases are attached to the 1'-C of the sugar, just as in the Watson-Crick model. However, each tetranucleotide component is a separate molecule, and the bases are directed to the outside.

All text material ©2024 by Steven M. Carr