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Mapping The Cannabis Genome Revealed Viral DNA That Split Cannabis Into Hemp and ‘Marijuana’

Emily Robertson
Bars of genetic code representing mapping the cannabis genome

University of Toronto researchers have just completed mapping the cannabis genome. This means opportunity for more directed research in cannabis medicine.

There’s much about cannabis that we still don’t know. Research has been limited, barred by the misguided classification of the plant as a Schedule 1 drug. This, for some countries, has even included Cannabis sativa’s non-psychoactive strain, hemp. But, with full legalization in Canada and across many states in America, research has finally opened up. This has allowed for mapping the cannabis genome.

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The University of Toronto recently published a press release describing their work on mapping the cannabis genome.  A key discovery was that hemp and ‘marijuana’ split into two different strains millions of years ago, after a virus attacked the plant. More on that in a moment.

Professor Tim Hughes of the Donnelly Centre for Cellular and Biomolecular Research completed the genome research with his team, including graduate student, Kaitlin Laverty. Hughes is also a senior fellow at the Canadian Institute for Advancement of Research.

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The Virus That Forced Genetic Separation of Hemp And Marijuana

The cannabis genome map has allowed researchers to understand that a virus colonized cannabis millions of years ago. This resulted in the separation of CBD-rich hemp and THC-dominant cannabis. CBD’s raw cannabinoid form, CBDa, and THC’s raw cannabinoid form, THCa, are synthase genes found on chromosome 6 of the 10 chromosomes of the cannabis genome.

These synthase genes are help to encode the enzymes to create THC and CBD and are surrounded by the viruses’ DNA. This made it difficult to differentiate the genome until current technology allowed researchers to magnify and separate them. These DNA are called retro-elements. These are copied millions of times until they have colonized the host and surrounded every site of the host’s DNA.

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Co-leader of the study, van Bakel described the occurrence of retro-element copies using an analogy of a jigsaw: “Plant genomes can contain millions of retro-element copies. This means that linking genes on chromosomes is analogous to assembling a huge puzzle where three quarters of the pieces are nearly the same colour. The combination of a genetic map and PacBio sequencing technology allowed us to increase the size of the puzzle pieces and find enough distinguishing features to facilitate the assembly process and pinpoint the synthase genes.”

Furthermore, the genetic sequences for CBDa and THCa are almost exactly the same and therefore likely stem from one gene. This gene was copied, then transformed by these retro-elements and by evolution. Genetic evidence has led researchers to believe that cannabis and hemp were differentiated because of these duplicating retro-elements and original synthase gene.

By mapping the cannabis genome, researchers also found the gene for the cannabinoid cannabichromene (CBC). CBC is now being researched for its anti-inflammatory properties. It may also be responsible for some of the psychoactive effects of cannabis, alongside THC.

What Does Mapping The Cannabis Genome Mean For Cannabis Research?

The genome map will help direct more research regarding the genetic make up of cannabis and hemp. Hughes explained that, “The chromosome map is an important foundational resource for further research which, despite cannabis’s widespread use, has lagged behind other crops due to restrictive legislation.” It will also help medical researchers learn how specific genes within the cannabis plant impart certain healing properties. Mapping the cannabis genome opens up the possibility of manipulating genes for optimal medicinal needs. For example, a cannabis plant that grows with  high CBDV concentration, a cannabinoid that has recently been found to stop seizures.

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This is just the start of exciting new research in cannabis that will change our knowledge about how cannabis interacts with the human body and how the plant itself exhibits so many healing properties.

Emily Robertson

Emily Robertson has been writing freelance and contract work since 2011. She has written on a variety of topics, including travel writing of North America and the growing legalized cannabis industry across the globe. Robertson has a master’s degree in literature and gender studies, and brings this through in her writing by always trying to explore different perspectives. Born and raised in southwestern Ontario, Robertson moved to Glasgow, Scotland in 2016 to undergo her doctorate in Scottish Literature. She lives in the West End with her dog, Henley.

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