Table 1. Base composition of each position in the 5′ end sequences.

Position	A	G	C	T	%purine	T/C
1	13,425	21,682	4,836	3,164	81	0.65
2	5,752	12,470	7,865	17,006	42	2.16
3	6,194	11,992	8,826	16,100	42	1.82
4	6,646	12,396	6,667	17,390	44	2.61
10	7,276	11,342	10,996	13,448	43	1.22
20	7,769	11,058	11,325	12,939	44	1.14

The occurrence of each base was counted at each position. The %purine was calculated as 100 × (A + G)/(A + G + C + T)