ANALYSIS OF CODON USAGE - POSITIONAL PREFERENCE IN VARIOUS ORGANISMS

The degree of preference of the four nucleotides C, G, A and U in the three positions I, II and III of the codons of 15137 genes of various individual organisms is examined using the nucleotide sequence data ob tained from the Gen Bank Genetic Sequence Data Bank (Release 65,0, Sep ., 1990). It is found that G, A and C, are preferred maximally in the three positions respectively. Similarly, U, G and A are preferred mini mally in these positions. The analysis shows a correlation in the posi tional base preference which discriminates against codons with the sam e base in all three positions or in the adjacent positions.