Genetic location of genes encoding cannabinoid synthases in Cannabis. Preliminary analysis of location and structure of the genes encoding CBCA synthase, CBDA synthase and multiple cannabinoid-synthase-like pseudogene copies in the hemp-marijuana hybrid cultivar ‘CBDRx’ (Grassa et al., 2018), which is the reference genome for Cannabis sativa. The genome has 9 pairs of autosomes and one pair of sex chromosomes, with the main locus of cannabinoid synthases located on chromosome 7 (green box, revised chromosome numbering (NCBI)) (a). Three different cassettes (1, 2 and 3, yellow regions with stripes) have been identified and mapped to a region on chromosome 7 between 24.5 and 31.5 Mb (b). The exact chromosomal arrangement is not clear, since the assembly contains gaps in between the different cassettes (grey boxes). Three cannabinoid synthase genes appear to have a full coding sequence: a CBCA synthase, the CBDA synthase and a CBDA-like synthase (*, black), while the other copies appear non-functional (grey). All sequences, including pseudogenes, have unique expression data associated with them (arrows, NBCI genome browser, unique raw reads). The synthases are encoded by one single exon (black) and surrounded by long terminal repeat retrotransposons (orange). Functional CBDA and THCA synthase share 83.86 % protein sequence similarity, while similarity amongst the other sequences ranges from 82 to 92 % (c). The CBDRx genome does not contain a functional THCAS, the sequence was acquired from uniprot (Q8GTB6). Gene density in (a) shows the ratio of the number of genes per million base pairs, calculated and plotted as an ideogram using RIdeogram (Hao et al., 2020). Gene annotation for the Y chromosome is not readily available, but genes are present (Prentout et al., 2020; McKernan et al., 2020). The CBDRx genome was derived from a female individual (Grassa et al., 2018), the size of the Y (*) chromosome was approximated from McKernan et al., 2020.