Table 2.

Most Significant Hexamers in 3′ Fragments: Clustered Hexamers

Hexamer	Observed (expected)a	% sites	Pb	Position average ± SD	Locationc
	3286 (317)	58.2	0	−16 ± 4.7
	843 (112)	14.9	0	−17 ± 5.3
	156 (32)	2.7	6 × 10−57	−16 ± 5.9
	180 (53)	3.2	4 × 10−45	−18 ± 7.8
	76 (23)	1.3	1 × 10−18	−17 ± 5.9
	72 (21)	1.3	2 × 10−18	−18 ± 6.9
	96 (33)	1.7	2 × 10−19	−18 ± 6.9
	70 (16)	1.2	5 × 10−23	−18 ± 8.7
	43 (14)	0.7	1 × 10−9	−18 ± 6.3
	49 (11)	0.8	5 × 10−17	−18 ± 8.9
	36 (11)	0.6	1 × 10−08	−17 ± 8.1

^aExpected occurrences based on a random distribution in a database of same nucleotide composition. 

^bProbability of reaching the observed frequency by chance based on a cumulative binomial distribution. All sequences containing the most significant hexamer were removed from the database before the next most significant hexamer was sought. 

^cLocation of the last base of hexamer. Position 0 is the putative poly(A) site.