A christmas tree version of the 'Backwards C' lab design with 100% GC bonds.
A "christmas tree" is a design that contains a high percentage of GC pairs. Sequences with an excessive amount of GC pairs are undesirable in lab, as they are difficult to synthesize and likely to misfold.
The very low energy of christmas tree designs often causes them to perform deceptively well in secondary structure prediction programs, including the package used to generate dot plots and melting plots in the EteRNA lab window.