To access the data, click or select the words “Appendix 2.” A) Bargain allele discovered in ENU mutagenesis screen. B) A replacement allele was generated by CRISPR-Cas9 mutagenesis, and sequencing confirmed a substitution of guanine by adenine (red rectangle), resulting in an early stop codon. An additional silent base substitution (purple arrow) was created to prevent “cut-back.” C) Predicted null protein product for both bargain and the CRISPR-generated replacement allele: a frame-shifted protein product beginning after amino acid 306 of the protein and terminating after the inclusion of 8 aberrant amino acids.