While this nature of the base distributions is found across many different sequences of eukaryotic genes, it is also very much evident in the case of viral sequences like the H5N1 neuraminidase which are known to mutate very rapidly; other plots from a sample of over 600 sequences of the H5N1 neuraminidase show similar quadratic forms. Interestingly, plots of the wheat, maize and chicken histone H4 genes, which are also intronless genes, can also be fitted by polynomials of degree 2, similar to the case of the viral genes. Chicken beta globin gene with intron sequences that are quite different compared to the mammalian genes plot in the first quadrant, but it also can be fit by a quadratic polynomial. This is however not true of all gene sequences. The mouse beta globin gene sequence representation in the 2D framework gives a very poor fit for the quadratic function (R 2 = 0.06) but much better statistics with a cubic polynomial (R 2 = 0.53) ( Table 1) ; the human delta globin gene also shows very good statistics when fitted with a cubic polynomial (R 2 = 0.98). Some sequences where significantly large segments are at variance with the overall pattern too cannot be put into such slots. The rat myosin heavy chain gene sequence where the intron sequences have been hypothesized to have grown through accretion of large fragments [30] , for example, presents a highly compact form on the 2D plot [15] and cannot be fit by the simple polynomials we have used so far. However, sufficiently large numbers of sequences are seen to follow the apparent quadratic relationship with good statistics that it is of interest to try to understand the underlying pattern.