Figure 3.

(Upper) Alignment of the nucleotide sequences of introns A, B, and 2 for D. sucinea and D. capricorni. Black shading over sites denotes identical nucleotides shared by at least two nonhomologous introns. Regions 1 and 2, denoted by light-shading overlay, indicate two regions of extensive site identity between the Drosophila introns. The two arrowheads indicate nucleotide substitutions between D. sucinea and D. capricorni. (Lower) Alignment of the nucleotide sequences of introns C and 2 in C. capitata.