RESUMO
Chicken repeat 1 (CR1) is a member of the non-long terminal repeat class of retrotransposons. We have isolated a truncated CR1 element within the third intron of the lactate dehydrogenase B gene of the coscoroba and the Cape Barren goose (Anseriformes; Coscoroba coscoroba, Cereopsis novaehollandiae). Because the element was absent in orthologous loci within mallard (Anas platyrhynchos), snow goose (Anser caerulescens), and tundra swan (Cygnus columbianus), it provides strong support to the recent novel proposal by Donne-Goussé et al. [Donne-Goussé, C., Laudet, V., Hänni, C., 2002. A molecular phylogeny of anseriformes based on mitochondrial DNA analysis. Mol. Phylogenet. Evol. 23, 339-356] that Cape Barren goose is the sister taxon to coscoroba. The time of insertion was approximately 10.5 Mya or less estimated from mitochondrial DNA sequence information. Because this is a recent event, the DNA sequence of this CR1 should be close to that existing at the time of its insertion. This is reflected by the consistency of several structural features expected in a new CR1 copy such as the unaltered flanking target site duplication and inverted repeats that lie 22 bp apart near the 3' end of the element. Hybridization experiments show that numerous copies of sequences closely related to the coscoroba CR1 element are dispersed throughout the genomes of tested Anseriformes, but none were detected in representatives of Galliformes and Struthioniformes.
