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Here is the current programme used by GW pharmaceuticals for gene-type selection in Cannabis breeding. The analysis of cannabinoid profiles and their synthetic precursors provides a basis for selection by chemo-type which is controlled by four independent loci.. By manipulating the parent genes at these four positions, breeders can precisely control the cannabinoid composition of the progeny..
![chemovars[0].jpg](/proxy.php?image=http%3A%2F%2Fwww.gwpharm.com%2Fuploads%2Fchemovars%5B0%5D.jpg&hash=acd7ac1f7ad7ebc16c051e340447f681)
The gene at locus O enables the production of the initial phenolic precursors (resorcinolic acids). These substituents combine with geranyl pyro-phosphate to create the intermediate cannabinoids CBG and/or CBGV, the central precursors for the end-product cannabinoids THC(V), CBD(V) and CBC(V). The functional allele O is co-dominant; O/o hybrids have a low cannabinoid content and o/o plants are cannabinoid-free.
The ratio of propyl and pentyl type cannabinoid precursors is determined by a postulated locus A, which is still under investigation. The CBG/CBGV intermediate is further processed by the alleles of locus B. BD and BT are co-dominant; the BD gene converts CBG(V) into CBD(V) and the BT gene converts CBG(V) into THC(V). In the BD/BT genotype, codominance allows the expression of a mixed CBD/THC chemotype. Also at this locus, non-functional alleles, designated B0 can exist; these are unable to convert the CBG(V) intermediate and leave the plant with a CBG(V) predominant chemotype.
Locus C remains fixed so all plants have CBC synthase activity. CBC synthase competes for the same CBG(V) precursor as the synthases encoded by locus B (THC and/or CBD synthase). In 'normal' Cannabis plants, CBC synthase is only active in the juvenile state. However, our scientists have discovered genetic factors that induce morphological mutations that are associated with a 'prolonged juvenile chemotype'. Prototype CBC production plants carry these factors in combination with B0/B0 at locus B. In these plants CBC synthase has no competition from THC or CBD synthase.
Source - http://www.gwpharm.com/default.aspx
[Meijer EPM de, Bagatta M, Carboni A, Crucitti P, Cristiana Moliterni VM, Ranalli P, Mandolino G. 2003. The inheritance of chemical phenotype in Cannabis sativa L. Genetics 163: 335–346.]
The gene at locus O enables the production of the initial phenolic precursors (resorcinolic acids). These substituents combine with geranyl pyro-phosphate to create the intermediate cannabinoids CBG and/or CBGV, the central precursors for the end-product cannabinoids THC(V), CBD(V) and CBC(V). The functional allele O is co-dominant; O/o hybrids have a low cannabinoid content and o/o plants are cannabinoid-free.
The ratio of propyl and pentyl type cannabinoid precursors is determined by a postulated locus A, which is still under investigation. The CBG/CBGV intermediate is further processed by the alleles of locus B. BD and BT are co-dominant; the BD gene converts CBG(V) into CBD(V) and the BT gene converts CBG(V) into THC(V). In the BD/BT genotype, codominance allows the expression of a mixed CBD/THC chemotype. Also at this locus, non-functional alleles, designated B0 can exist; these are unable to convert the CBG(V) intermediate and leave the plant with a CBG(V) predominant chemotype.
Locus C remains fixed so all plants have CBC synthase activity. CBC synthase competes for the same CBG(V) precursor as the synthases encoded by locus B (THC and/or CBD synthase). In 'normal' Cannabis plants, CBC synthase is only active in the juvenile state. However, our scientists have discovered genetic factors that induce morphological mutations that are associated with a 'prolonged juvenile chemotype'. Prototype CBC production plants carry these factors in combination with B0/B0 at locus B. In these plants CBC synthase has no competition from THC or CBD synthase.
Source - http://www.gwpharm.com/default.aspx
[Meijer EPM de, Bagatta M, Carboni A, Crucitti P, Cristiana Moliterni VM, Ranalli P, Mandolino G. 2003. The inheritance of chemical phenotype in Cannabis sativa L. Genetics 163: 335–346.]
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