Plant genetics can be coached to express varying concentrations of cannabinoids, but the relative ratios of the key cannabinoids, THCA and CBDA, are usually genetically determined. As an example, there are no known agricultural methods to make a CBDA-dominant strain become a THCA-dominant strain via environmental conditions. These critical chemotypes are governed by gene knockouts in their respective enzymatic synthases (CBDA Synthase and THCA Synthase).


Use Genetic Screening to Determine Plant Type

Most cannabis plants can be classified into four groups based on their cannabinoids profiles: THCA-dominant Type I plants, THCA:CBDA hybrid Type II plants, CBDA dominant Type III plants, and CBG-dominant Type IV plants. Cultivators can use genetic screening tools that detect whether the THCA synthase gene and/or the CBDA synthase gene is present in a plant. Different combinations of results on the respective tests will indicate the plant type. 

Type I Plant

Type I Plant


Type II Plant

Type II Plant


Type III Plant

Type III Plant


Type IV Plant

Type IV Plant


*Plants that test negative for THCA or CBDA may still produce low percentages (<2%) of either compound.

Powered by youPCR®

Medicinal Genomics offers THCA synthase and CBDA synthase detection tests that run on the youPCR® Plant Screening Platform. Plant DNA is obtained from a small hole punch in the leaf. If the DNA sample contains the target sequence, a chemical reaction will turn the pink solution yellow, indicating a positive result.

youPCR Results photo

Available Cannabinoid Screening Products

Item # Name Reactions
420212 youPCR® Solution B – CBDA 50 Buy Now
420214 youPCR® CBDA Positive Control 50 Buy Now
420217 youPCR® Solution B – THCA 50 Buy Now
420218 youPCR® THCA Positive Control 50 Buy Now

Getting Started with youPCR is as easy as 1, 2, 3.

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Frequently Asked Questions

Can I use youPCR® to test seeds?

No. Although we have done some initial research into using youPCR® to test seeds, we have not done enough to confidently say it works as well as testing leaf. We recommend sampling a seedling’s first set of true leaves when using youPCR®.

Can I use youPCR® to determine cannabinoid percentages?

youPCR® assays provide a positive/negative result. When using youPCR® to screen for CBDA or THCA synthase, a positive result means there is an active CBDA or THCA synthase allele. Unfortunately, that result can’t be used to predict what percentage the plant will ultimately produce. However, if you combine the CBDA and THCA tests you can determine the plant type.

  • Type I Plant (THCA-dominant) = THCA(+) CBDA(-)
  • Type II Plant (THCA:CBDA hybrid) = THCA(+) CBDA (+)
  • Type III Plant (CBDA-dominant) = THCA(-) CBDA(+)
  • Type IV Plant (CBGA-dominant) = THCA(-) CBDA(-)
Does a negative result on the youPCR® THCA Synthase Assay mean my plant will produce less than .3% THC?

No. Plants that test negative for THCA or CBDA may still produce low percentages (<2%) of either compound.

Can I use the youPCR® Gender Assay to detect hermaphrodites?

No. Cannabis plants typically hermie as a response to stress. Although there may be genetic markers that determine if a plant is more likely to hermie, we have not found them, and we do not target them with our gender test. The youPCR® Gender Assay specifically looks for a Y chromosome.

Are all the necessary consumables and equipment included in the youPCR® starter kits?

The youPCR® Starter Kits do not include PCR Thermal Cyclers. We recommend the following models:

  • miniPCR. Use Promo Code “MGC” to receive a discount off list price.

The youPCR® Starter Kits also do not include chemical reagents: Solution A, Solution B, Solution C, and Positive Control. Those must be purchased separately on the Medicinal Genomics web store.

What basic laboratory experience do I need to run youPCR® tests?

In order to successfully test with youPCR®, you should have experience with the following laboratory techniques/best practices:

  • Liquid handling with a pipette
  • Benchtop sterility techniques
  • Proper disposal of tips, punches, strip tubes
Are Medicinal Genomics products ISO certified?

All of the chemicals and reagents we sell in our webstore are manufactured in facilities that are certified to ISO 9001 and/or ISO 13485 standards.

Still have questions? Don’t hesitate to reach out to us.