Tag Archives: DNA

An Introduction to Cannabis Genetics, Part I

By Dr. CJ Schwartz

What is DNA?

DNA stores information about how to build an organism. Just as a series of 0’s and 1’s represents digital data, DNA data is represented by four letters (A, C, G and T), which inherently allows DNA to store more information per unit (Figure 1).

Figure 1
Figure 1

The amount of DNA required to build a human is mind-boggling. The human genome has 3.2 billion A’s, C’s, G’s, or T’s, (called nucleotides). Cannabis has 820 million nucleotides. This is true for every cell in the organism. The DNA from a single human cell when spread out would stretch six feet long. A cell is not visible to the naked eye, yet it contains a microscopic thread of DNA six feet long! If you put all the DNA molecules in your body end to end, the DNA would reach from the Earth to the Sun.

DNA is common in all living things, and all living things are related through DNA. Humans and plants share 50% of their genes. In humans, 99.9% of the DNA is identical, thus just 0.1% of DNA differences accounts for all of the variation observed in humans. Cannabis, as a species, is more variable with approximately 1% of the DNA being different among strains. DNA is a super efficient and reliable information storage system. However, mistakes (mutations) do occur and while infrequent, these mutations account for all the differences observed within a species and is called natural genetic variation. Variation within the genomes of a species can help the species survive in unfavorable conditions (evolution) and is also the source of differences in traits, which is the material that is required for successful breeding.

Natural Genetic Variation

DNA mutations occur in every generation and these changes will be different in each individual creating natural genetic variation. Mutations (or more accurately referred to as DNA changes) will be inherited by offspring and will persist in the population if the offspring reproduce.

Figure 2
Figure 2

DNA differences maintain diversity in the gene pool, allowing organisms to respond to new environments (migration) or environmental changes (adaptation). The two most commonly described cannabis families are Indicas and Sativas. Indicas, being from cooler temperate regions, have wide leaves allowing the maximum capture of light during the shorter growing season. Sativas, being equatorial, have smaller leaves, which may be an advantage for such things as powdery mildew in a humid environment. Figure 2 shows the enormous amount of natural variation in leaves for one species with a worldwide population (Arabidopsis thaliana).

A DNA change that occurred a long time ago will be more useful to divide people/plants into different groups. For example, there are ancient DNA changes that differentiate humans originating from Europe or Asia. Other newer DNA changes allow us to further divide Europeans into those originating from Northern versus Southern Europe. Thus, different DNA changes have different values for determining relatedness or ancestry, yet every DNA change provides some information for determining heredity.

Figure 3
Figure 3

Family Trees

By comparing DNA changes among different strains, we can measure the relatedness between strains. For example, if strain A has a DNA change indicative of Kush ancestry and strain B has a DNA change indicative of hemp ancestry, we can assign strains to branches of the cannabis family tree comprised of strains that contain similar DNA changes. Figure 3 shows 184 strains that have been characterized for these changes, and the position of each strain is based on its shared DNA with neighboring strains. The two best-defined families of cannabis are hemp (blue) and kush (black). Strains within a family are more closely related. Strains in separate families, such as kush and hemp, are more distantly related.


Editor’s Note: This is the first installment in a series of articles focused on answering common questions regarding cannabis genetics. If you have questions regarding cannabis genetics, or wish to speak more about the topic please post in the comments section below. The next installment will delve into the THC synthase, gene discovery and manipulation and mapping chromosomes.

Researching Cannabis Genetics: A Q&A with CJ Schwartz, Ph.D.

By Aaron G. Biros

Studying cannabis genetics is a convoluted issue. Strain classification, medicinal effects and plant breeding are particular areas in the science of cannabis that still require heavy research. Marigene, a company researching cannabis genetics, is currently working with universities and research institutes to help map the cannabis genome and catalog genetic variation.

CJ Schwartz, Ph.D.

According to CJ Schwartz, Ph.D., chief executive officer and founder of Marigene, their mission is to “to classify, certify, and improve cannabis.” After studying genetics and cellular biology at the University of Minnesota, Schwartz received his Ph.D. in biochemistry from the University of Wisconsin. His research in the past decade has focused on genetic variations that control flowering time, discovering the expression of a gene called Flowering Locus T leads to differential flowering time of plants and is dependent on their native locations. We sat down with Schwartz to learn more about his research and collaborative efforts.

Cannabis Industry Journal: Why are you researching mapping the cannabis genome?

CJ Schwartz, Ph.D: We seek to identify the genetic differences among cannabis strains and the genes responsible for these differences. Genetic differences are what cause different strains to have different effects. DNA allows reproducibility, consistency, and transparency for your cannabis strains.

The more information we gather about cannabis genetics, the more tools we have available to create tailored strains. Cannabis is a targeted compound. It interacts with a very specific system in the human body, similar to hormones, such as insulin. Understanding the cannabis genome will help bring legitimacy and integrity to cannabis products, and allow us to better understand how chemicals from cannabis interact with the human brain. Genetic identification can provide a method of certification to more comprehensively describe plant material.

Schwartz doing sample preparation on the lab bench.
Schwartz doing sample preparation on the lab bench.

CIJ: How did you get involved in cannabis research?

Schwartz: My interest in cannabis guided my research career. Cannabis may not be a cure-all, but it has significant and measurable medicinal effects for many patients.

To allow true development of cannabis products, we need more science! Our genetic analysis is required for normalization and acceptance of cannabis products, but also essential for future breeding efforts to develop better and more useful plants.

Our sister company, Hempgene, is applying all of the same technology and techniques for hemp research. One focus of Hempgene is to manipulate flowering time in select hemp cultivars so that they mature at the appropriate time in different environments.

CIJ: What do you hope to accomplish with your research?

Schwartz: We can develop or stabilize a plant that produces a very specific chemical profile for a specific condition, such as seizures, nausea or pain. By breeding plants tailored to a patient’s specific ailment, a patient can receive exactly the medicine that they need and minimize negative side effects.

The current term describing the interaction of cannabis compounds is called the entourage effect. Interactions among compounds can be additive or synergistic. The entourage effect describes synergistic effects, where small amounts of compound A (e.g. Myrcene) vastly increase the effects of compound B (e.g. THC). Instead of flooding one’s body with an excessive amount of chemicals to get a non-specific effect, cannabis plants can be bred to produce a very specific effect.

A view of some of the work stations inside the laboratory at Marigene.

Currently our goal is to catalog the natural genetic variation of cannabis, and to identify DNA changes that affect a trait of interest. Once superior variants of a gene are identified, those variants can be combined, by marker-assisted breeding, to produce new combinations of genes. How different cannabis chemicals interact to produce a desired effect, and how different human genetics influence the efficacy of those chemicals should be the ultimate goal of medical marijuana research.

We are working closely with academic institutions and chemical testing labs to gather data for establishing correlations between specific cannabis strains and desirable chemical profiles. Our closest collaborator, Dr. Nolan Kane at UC-Boulder, is working to complete the Cannabis genomic sequence and generate the first high- resolution cannabis genetic map.

We are currently accepting samples and we produce a report in roughly two to three months. For one sequencing run, we identify 125 million pieces of DNA that are 100 base pairs long. We get so much information so there is a considerable time commitment.