Cysteine codon 234 (TGT) was targeted for change to a tryptophan codon (TGG)(p.C234W) with an sgRNA (targeting GTCTTCCTATATGATGACGC) and an ssODN template (TTTCCCTTCGGCTGGCTCATCTTCCAGTCTTCCTATATGATGACGTTAGTC). The mutation selectively abolishes the enzymatic activity needed to process C22 polyunsaturated fatty acids, while leaving other enzymatic activity intact. (J:284063)