Table 3. Comparisons of CRX sequences by exon across species (percent identity).

A. 5′ UTR (non-coding)
	Z EXON 1	H EXON 1	M EXON 1	D EXON 1
Z EXON 1	100	55.5	47.6	49.3
H EXON 1		100.0	69.2	66.2
M EXON 1			100.0	60.0
B. 5′ UTR + Coding
	Z EXON 1	H EXON 2	M EXON 2	D EXON 2
Z EXON 1	100.0	56.0	57.1	55.6
H EXON 2		100.0	84.4	87.6
M EXON 2			100.0	75.5
C. Coding
	Z EXON 2	H EXON 3	M EXON 3	D EXON 3
Z EXON 2	100.0	74.3	69.7	73.0
H EXON 3		100.0	90.8	88.2
M EXON 3			100.0	88.9
	Z EXON 3	H EXON 4	M EXON 4	D EXON 4
Z EXON 3	100.0	56.4	53.0	57.2
H EXON 4		100.0	87.0	88.8
M EXON 4			100.0	84.7
D. 3′ UTR (non-coding)
	Z EXON 3	H EXON 4	M EXON 4	D EXON 4
Z EXON 3	100.0	41.6	33.6	42.5
H EXON 4		100.0	44.9	48.1
M EXON 4			100.0	45.6

Cross-species sequence comparisons of Crx. The three identified exons in zebrafish Crx share sequence identity with all the four identified exons in the mammalian CRX genes. A: Zebrafish Crx Exon 1 shares a region of moderate sequence identity with human, mouse and dog Crx Exon 1 in the non-coding, 5′ untranslated region. B: A second region of zebrafish Crx Exon 1 shares slightly higher sequence identity with human, mouse and dog Crx Exon 2. This slight increase in sequence identity is attributable to the high sequence identity within the coding regions. C: The coding regions in Zebrafish Crx Exon 2 and the mammalian Exon 3 and zebrafish Exon 3 and the mammalian Exon 4 share the highest sequence identity. D: The lowest level of identity is in the non-coding, 3′ untranslated regions of zebrafish Crx exon 3 and the mammalian CRX exon 4. These comparisons used sequences from zebrafish (“Z”; Danio rerio; AF0503443); human (“H”; Homo sapiens; BC016664, BG396702); mouse (“M”; Mus musculus; AK053533); dog (“D”; Canis familiaris; AF454668).