Example of songbird novel and duplicated genes associated with regions of syntenic disruption. Chromosomal maps of the syntenic order of genes in chicken (chr1) compared to Zebra finch (chr1A) reveal that songbird-unique de novo novel gene (TMRA, in orange) and duplicated/expanded novel genes (CASC1, A4GALT; in red) are located in chromosomal regions containing syntenic disruptions (SD) that are unique to the songbird lineage (i.e. the syntenic flanking genes in Zebra finch are different from those in other avian and non-avian species). Small black up/down arrows next to each gene indicate orientation on the minus/plus strand of DNA. Line colours denote genes in rearranged syntenic blocks, with shaded regions representing apparent chromosomal inversions.