Table 1.

Convergence of SP1 Cis-Regulatory Conversions within Birds and Placental Mammals

	Human GC Box			Human GA Box
	Obs.a	Expb	Pc	Obsa	Expb	Pc
Mammal root: GA boxd
Bird GC box	63	43	5.7e−5e	55	55	0.32
Bird GA box	47	48	0.39	83	61	1.6e−5
Mammal root: GC boxd
Bird GC box	109	90	2.6e−4	37	34	0.17
Bird GA box	51	45	0.06	27	17	3.0e−4

^aThe observed numbers of GA/GC box co-occurrences across orthologous genes.

^bThe expected number of GA/GC box co-occurrences, assuming a random distribution of motifs without regards to gene orthology.

^cP values representing the significance of enrichment using Fisher’s exact test.

^dGenes are separated according to the motif inferred in the common mammalian ancestor; genes inferred to contain both motifs at the root of mammals have been excluded.

^eGenes in this category have gained a GC box independently along the human and bird lineages; no GC box was present at the root of mammals.