Table 1.

Tests for significance for phase zero positions

Data set	No. of positions	Excess in module boundaries, %	P
Overall intron density
d = 2	94	24.9	0.05
d = 4	350	19.5	0.011
d = 6	611	17.4	0.0044
d = 8	991	13.0	0.016
All phase zero	3,328	6.7
No. of homologs
h = 1	38	53.8	0.0058
h = 5	206	34.8	0.0001
h = 10	610	14.7	0.0023
h = 20	1,132	8.4	0.26
All phase zero	3,328	6.7

P values are based on 10,000 random samples of the given size. P values in italics are significant at the P = 0.05 level.