Table 3.

Differential expression levels measured using the four largest X. laevis EST sets show that a significant fraction doublets show differential expression.

EST library	ESTs	ESTs hitting probes	Number of probes hit	N > = 16	P < = 0.01
ANE	69917	9988	1092	130	53
NIBBegast	40476	5424	1199	40	20
NICH_brain1	11005	1278	478	12	2
XGC_Kid1	9662	1504	573	9	3

A total of 2070 matched pairs of antisense "probes" were computed as described in Methods, and applied to the EST data by in silico hybridization. Genes with 16 or more hits to ESTs were used to test the null hypothesis that expression levels are the same between paralogs. The four libraries are: ANE (anterior neuroectoderm) [36]; NIBBegast (early gastrulation; Kityama, A, Terasaka, C, Mochii, M, Ueno, N, Shin-i, T, unpublished results); NICH_brain1 (brain; NIH Mammalian collection, unpublished results); and XGC_kid1 (kidney; Heil, O, Neubert, P, Peters, M, Radelof, U, Schneider, D, Schroth, A, Korn, B, Landgrebe, J, unpublished results).