Gene order and orientation in regions surrounding NAT genes on chicken ( Gallus gallus ) chromosome 11, turkey ( Meleagris gallopavo ) chromosome 13 and zebra finch ( Taeniopygia guttata ) chromosomes 11 and Un. Gene lengths and intergenic distances are not drawn to scale. Grey boxes indicate NAT-like sequences. Black boxes represent chicken-specific genes with no homologous sequences in turkey or zebra finch. Double slashes (//) indicate continuing sequence data extending toward the centromeric (cen) and telomeric (tel) parts of the chromosome. In each species, NAT genes are arrayed linearly along a single chromosome, indicating an expansion of the NAT gene family through tandem repeats, except in zebra finch where a fifth copy is found on an unidentified (Un) chromosome. Chicken NAT4 (chr11:17,483,758-17,484,630 in galGal3 assembly) represents a short sequence of 873 bp, identical to the NAT3 protein-coding sequence, which is embedded within the NAT3 gene (chr11:17,481,972-17,493,917) upstream of the NAT3 coding sequence.