# Chemotype

> A chemotype is a plant's chemical phenotype, in cannabis usually its dominant cannabinoid class: THC-dominant (I), mixed (II), CBD-dominant (III), CBG-dominant (IV) or cannabinoid-free (V).

- Canonical: https://genetixbay.com/knowledge/glossary/chemotype.html
- Also written: chemotypes, chemical phenotype, cannabinoid chemotype, chemotype I, chemotype III
- Glossary category: Genetics and breeding · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

A chemotype is the chemical phenotype of a plant. In cannabis research it normally means the [cannabinoid](https://genetixbay.com/knowledge/glossary/cannabinoid.md) class, set largely by the [alleles](https://genetixbay.com/knowledge/glossary/allele.md) at the cannabinoid synthase locus. The usual scheme: chemotype I is THC-dominant, II is mixed [THC](https://genetixbay.com/knowledge/glossary/thc.md) and [CBD](https://genetixbay.com/knowledge/glossary/cbd.md), III is CBD-dominant, IV is CBG-dominant, and V has almost no cannabinoids (de Meijer et al. 2003; de Meijer et al. 2009).

## In practice

Chemotype is the first thing to fix in a medicinal or hemp line and the easiest to test early. Breeders can screen seedlings with a DNA marker for the synthase alleles (Toth et al. 2020) and keep only the wanted chemotype before flowering. A THC-dominant × CBD-dominant cross gives uniform type II [F1s](https://genetixbay.com/knowledge/glossary/f1.md); their [F2s](https://genetixbay.com/knowledge/glossary/f2.md) segregate back into I, II and III.

Some writers extend "chemotype" to [terpene profile](https://genetixbay.com/knowledge/glossary/terpene-profile.md) ("a limonene chemotype"). That use is looser and less standardised; terpene profiles are controlled by many genes and shift with growing conditions.

## Don't confuse with

- **Chemovar**: a named cultivar defined by its chemistry. A chemotype is a class; a [chemovar](https://genetixbay.com/knowledge/glossary/chemovar.md) is a variety.
- **Potency**: chemotype is the type of cannabinoid, not how much. Two type I plants can test 12% or 25%.
- **Indica or sativa**: these labels do not predict chemotype (Smith et al. 2022).

## Related terms

[Chemovar](https://genetixbay.com/knowledge/glossary/chemovar.md), [Codominant](https://genetixbay.com/knowledge/glossary/codominant.md), [Phenotype](https://genetixbay.com/knowledge/glossary/phenotype.md), [Allele](https://genetixbay.com/knowledge/glossary/allele.md), [Genotyping](https://genetixbay.com/knowledge/glossary/genotyping.md)

## Read more

- [Chemotype inheritance: how THC and CBD synthase alleles pass on](https://genetixbay.com/knowledge/breeding/chemotype-inheritance.md)

## Sources

1. de Meijer EPM, Bagatta M, Carboni A, et al. 2003. The inheritance of chemical phenotype in Cannabis sativa L. Genetics 163(1):335-346. https://doi.org/10.1093/genetics/163.1.335
2. de Meijer EPM, Hammond KM, Sutton A. 2009. The inheritance of chemical phenotype in Cannabis sativa L. (IV): cannabinoid-free plants. Euphytica 168:95-112. https://doi.org/10.1007/s10681-009-9894-7
3. Toth JA, Stack GM, Cala AR, et al. 2020. Development and validation of genetic markers for sex and cannabinoid chemotype in Cannabis sativa L. GCB Bioenergy 12(3):213-222. https://doi.org/10.1111/gcbb.12667