Figure 1.

χ² values for individual positions of Alu and ID flanking repeats and of adjacent regions. χ² = Σ_{i = 1}⁴(O_i − E_i)²/E_i; E_i = (Total) × (Composition_i), where individual base occurrences (O_i), total numbers of bases at different positions (Total), and the base compositions (Comp.) for the top and bottom part of the figure are from Tables 1 and 2, respectively. χ² values above the broken horizontal line correspond to significance levels of P < 0.001 for 3 degrees of freedom. The discrete χ² values were connected by lines to improve the presentation. (a) A cluster of significant χ² values occurs at positions −2 through +4 around the 5′ ends of flanking repeats. (b) Significant χ² values are near the 3′ ends of flanking repeats at positions −4, −3, and −2 immediately preceding the presumed antisense nicking site which is between positions −1 and +1. The significant nonrandomness around positions −11 through −16 corresponds to the 5′ end of flanking repeats presented above. Significant χ² values not shared by Alu and ID flanking repeats are not considered here. (c) The overall scheme indicating mutual orientation of retroposed elements, flanking repeats, and adjacent regions.