CEACAM1 and CEACAM28 genomic regions involved in gene conversion. The 2332 bp genomic region of CEACAM1 which covers nearly 1 kb of the 5'-flanking region (5'-FR), the leader exon (L), intron 1 (IntI), the N domain exon (N) and part of intron 2 (Int II) is highly conserved in CEACAM28 (99%) and, therefore, probably participated in a recent gene conversion event. The homologous sequences upstream and downstream from the conserved region are less conserved (80% and 92%, respectively) (A). This can also be deduced from the degree of conservation of the amino acid sequences encoded by the leader, N and A domains which is much less outside of the gene conversion region. Note that CEACAM28 contains two A2 type domains (B).