# CBGA

> CBGA (cannabigerolic acid) is the precursor cannabinoid that the plant converts into THCA, CBDA or CBCA, formed by joining olivetolic acid to geranyl pyrophosphate.

- Canonical: https://genetixbay.com/knowledge/glossary/cbga.html
- Also written: CBG-A, cannabigerolic acid, mother cannabinoid, precursor cannabinoid
- Glossary category: Cannabinoids and terpenes · 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"

CBGA, cannabigerolic acid, is the branch point of [cannabinoid](https://genetixbay.com/knowledge/glossary/cannabinoid.md) biosynthesis. A prenyltransferase enzyme attaches a ten-carbon geranyl group (from geranyl pyrophosphate) to olivetolic acid, producing CBGA in the [trichome head](https://genetixbay.com/knowledge/glossary/trichome-heads.md). Three oxidocyclase enzymes then compete for it: [THCA synthase](https://genetixbay.com/knowledge/glossary/thca-synthase.md) makes [THCA](https://genetixbay.com/knowledge/glossary/thca.md), [CBDA synthase](https://genetixbay.com/knowledge/glossary/cbda-synthase.md) makes CBDA and CBCA synthase makes CBCA. Whatever isn't converted stays as CBGA.

## In practice

That competition is why the [THC:CBD ratio](https://genetixbay.com/knowledge/glossary/chemotype-ratio.md) is mostly a genetic trait. A plant's synthase alleles decide where the CBGA goes. Growers sometimes call CBGA the "mother cannabinoid", a convenient image but chemically it is simply the shared precursor. [Decarboxylation](https://genetixbay.com/knowledge/glossary/decarboxylation.md) turns any remaining CBGA into [CBG](https://genetixbay.com/knowledge/glossary/cbg.md).

## Don't confuse with

- **CBG**: the neutral form, after decarboxylation.
- **Olivetolic acid**: one of CBGA's two building blocks, not a cannabinoid itself.
- **CBGVA**: the propyl (C3) analogue, made from divarinic acid, which leads to THCVA and CBDVA.

## Related terms

[CBG](https://genetixbay.com/knowledge/glossary/cbg.md), [THCA synthase](https://genetixbay.com/knowledge/glossary/thca-synthase.md), [CBDA synthase](https://genetixbay.com/knowledge/glossary/cbda-synthase.md), [Olivetolic acid](https://genetixbay.com/knowledge/glossary/olivetolic-acid.md), [Geranyl pyrophosphate](https://genetixbay.com/knowledge/glossary/geranyl-pyrophosphate.md), [Chemotype ratio](https://genetixbay.com/knowledge/glossary/chemotype-ratio.md)

## Read more

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

## Sources

1. Gülck T, Møller BL. 2020. Phytocannabinoids: origins and biosynthesis. Trends in Plant Science 25(10):985-1004.
2. Sirikantaramas S, Morimoto S, Shoyama Y, et al. 2004. The gene controlling marijuana psychoactivity: molecular cloning and heterologous expression of Δ1-tetrahydrocannabinolic acid synthase from Cannabis sativa L. Journal of Biological Chemistry 279(38):39767-39774.
3. Taura F, Sirikantaramas S, Shoyama Y, et al. 2007. Cannabidiolic-acid synthase, the chemotype-determining enzyme in the fiber-type Cannabis sativa. FEBS Letters 581(16):2929-2934.