Image of two fly heads. The left one has normal eyes, while in the right one the eye is degenerated. Eye degeneration is caused by eye specific expression of a RNAi construct against eyes absent (eya), an essential gene for eye morphogenesis. The eya RNAi construct is located on the vector backbone of the donor plasmid that was used in this CRISPR knock-in experiment.
Chasing donor backbone insertions in #CRISPR knock-in experiments is a great way to waste an afternoon (or more), unless you use a dominant marker. We like this one from the Carthew lab, in which animals containing the backbone have degenerated eyes:
www.tandfonline.com/doi/full/10....
#Drosophila