Table 2.

Raw and Normalized ESE Density (ND) in Putative Retrocopies, in Other Intronless Sequences, and in the Full Set of Intronless Genes.

	Full Data Set	Without Broad Set Retrocopies	Broad Set Retrocopies Only
Median raw ESE density	≈0.131	≈0.121	≈0.156
Median ND	≈0.253	≈0.233	≈0.275
P value for enrichment over expecteda	≈0.004	≈0.015	≈2.000 × 10−4
Sample sizeb	157 data points (344 genes)	122 data points (262 genes)	50 data points (82 genes)

^aHere, the P value is the probability that an ESE density this high or higher could have been obtained by chance given the nucleotide composition of the sequences. It was computed separately for each set and does not pertain to a comparison between sets.

^bThe sample size differs from the number of genes because each data point corresponds to a paralogous family rather than to a single gene (see Materials and Methods). The clustering into families was performed independently for each data set.