Table 2.

Summary of old exons and new exons (I and N) and their evolution patterns

	Exon no.	Mean len for K_a, K_s	Mean EST no. in mouse	Mean EST no. in human	Indel/kb	K_a	K_s	K_a/K_s	% of K_a/K_s > 1
Total exons in mouse/rat	71,039	147.3	10.0	12.7	0.37	0.027	0.171	0.155	2.53
Old exons in mouse/rat/human	64,760	142.9	10.0	12.6	0.31	0.025	0.172	0.143	2.17
I exons	1709	255.2	4.7	0	0.86^*	0.049^*	0.169	0.290^*	6.50^*
N exons	986	124.5	4.2	0	1.35^*	0.066^*	0.180	0.367^*	14.00^*
I old sister exons	9951	146.0	7.2	8.3	0.35	0.028	0.170	0.166	2.67
N old sister exons	3608	147.0	6.5	7.2	0.59	0.045	0.180	0.248	5.57

See text for I and N.
↵* In K_a indicates significant both in 95% CI and distribution tests. ^* In other items indicates significant in ϰ² test. Len refers to length in base pairs.

Origin and evolution of new exons in rodents