On the other hand, the avian sister group of crocodilians retained only CR1 group A activity (but see supplementary fig. S3, Supplementary Material online, for low-copy relics of CR1 group F).
We define a TGA as a structure of contiguous paralogous gene copies, which are either functional or degenerated copies (gene relics), allowing for the presence of one heterologous gene inserted between the two homologous copies.
Seventy-one copies are relics with degenerate CDSs and no more than one TIR or have an intact CDS that is associated with a single TIR.
Scientists have long used CT scans to peek inside fossil-bearing rocks, but the increasing use of 3D printers now enables them to make endless numbers of exact copies of those relics.
The number of repeats is high when the cas system is complete, intermediate when the erosion of the system is recent and reduced to a few copies when only relics of the system are detectable (Figure 1D).
One relic copy has also been identified in D. melanogaster [ 22].
Finally, L. cidri contains only a relic copy: Its genome has removed all the functional copies of Rover.
An additional pair of fixed copies could be identified; it is composed of a TIR-free transposase and a relic copy in L. dasiensis and L achancea meyersii, respectively.
Even in L achancea cidri, where only one relic copy still exists, the copy is located at the extremity of a synteny block shared with L achancea fermentati, L. cidri's closest relative.
This divergence may result in diversification and the formation of new families or produce defective copies such as miniature copies, TIR-free transporases, orelicscs (Kidwell and Lisch 2001).
Others are ancient with many relic copies (e.g., Dromar2 and Dromar10).
