Here, for the first time, the structure of genes involved in sex determination in mammals (full and partial , , and ) was analyzed for the European mole with ovotestes in females. We confirmed male-specificity for and . Five exons were revealed for and the deep similarity with the structure of this gene in was proved. The most intriguing result was obtained for the gene, which, in placental mammals, initiates male development. We described two exons for this canonically single-exon gene: the first (initial) exon is only 15 bp while the second exon includes 450 bp. The exons are divided by an extended intron of about 1894 bp, including the fragment of the LINE retroposon. Moreover, in chromatogram fragments, which correspond to intron and DNA areas, flanking both exons, we revealed double peaks, similar to heterozygous nucleotide sites of autosomal genes. This may indicate the existence of two or more copies of the gene. Proof of copies requires an additional in-depth study. We hypothesize that unusual structure and possible supernumerary copies of may be involved in ovotestes formation.
