Nature and diversity of amino acid abundance trends near exon-intron boundaries. Relative abundance of glutamine (Q), methionine (M), and lysine (K) as a function of distance from the boundary across 5' ends of D. melanogaster exons is shown. Glutamine is significantly avoided near the boundary (rho = 0.86, P < 1.84E-7), lysine is preferred (rho = -0.65, P < 6.2E-5), whilst no significant trend is evident for methionine (rho = 0.096, P = 0.59). Note that a negative slope/rho value indicates a preference near the exon-intron boundary. Typically, where patterns of preference/avoidance are evident, we observe quasi-monotonic decreases/increases in relative abundance across the sequence range analyzed.