The Lemon mutation is an A to G transition at base pair 3,746,768 (Build 38) on Chromosome 4, which is base pair 68,648 of the genomic region containing Lyn (GenBank NC_000070). The mutation, in the seventh of the gene's 13 exons, corresponds to nucleotide (nt) 794 of the mRNA sequence (NM_001111096) encoding the long isoform of the LYN protein (Lynp56) and to nt 731 of the transcript (NM_010747) encoding the short protein isoform (Lynp53). Alternative splicing of exon 2 produces mRNAs encoding the two protein isoforms, which differ at their amino (N) termini; Lynp56 is 21 amino acids longer than Lynp53. The Lemon mutation results in a histidine (H) to arginine (R) substitution at position 182 (H182R) in the Lynp56 (ENSMUSP00000038838) isoform and at position 162 (H162R) in the Lynp53 (ENSMUSP00000100075) isoform.