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14. Inject all of the embryos with solution 1 (e.g. MO), no phenol red. Be sure to immediately remove uninjected or damaged embryos, so that all remaining embryos are known to be injected. Next, inject every other embryo with solution 2 (e.g. RNA), with phenol red. Separate red and non-red embryos to be the double-injected and single-injected groups, respectively.
References
Gene Tools' essential informationUseful Documents page.
Review on using morpholinos: JS Eisen and JC Smith (2008), "Controlling morpholino experiments: don't stop making antisense". Development, 135:1735-43. (free download from Development website).