Figure 4.

Primate and candidate rodent KCNMB3 1b exons probably arose independently and neither appear to be conserved among mammals. In A, the indicated genomes were compared using the UCSC genome browser for homologies to a segment from the cloned human KCNMB3 1b exon (Uebele et al., 2000) but also including 10 bases preceding the beginning of the presumed 1b ORF. Segments of homology are only observed in chimp and rhesus monkey, both of which also share a consensus sequence (red box) appropriate for an intron–exon junction just preceding the ORF. In B, the indicated genomes were compared for segments homologous to the 122 base pairs in the cloned putative mouse 1b exon, with no segments of homology found in any other mammalian genome. The candidate mouse 1b exon is preceded by an appropriate intron–exon splice site.