Genotype is based on the DNA of an organism. Cannabis is diploid, meaning that it inherits two copies of each gene — one copy from each parent. Thus, the genotype for a gene of interest is based on the combination of the two copies.

Phenotypes are the observable characteristics or traits of a plant that are determined by genotype and physical environment (including but not limited to temperature, humidity, and cultivation practices). Some phenotypes — like leaf shape and flower color– can be seen, whereas others — such as the chemotype of a plant (the chemical phenotype, like terpene profile and cannabinoid potency) — can only be measured.

Cannabis genetics work similarly: one parent plant may be broad-leafed with low levels of THC, while the other is narrow-leafed with high levels of THC. Their children — the seeds — will contain genetics from both parents, and only some of those traits will express themselves when the plant actually grows. This is why the morphology of the plant — or the way it looks — is not a sufficient indication of its chemical content.

Nor, however, is genetics — even clones of the exact same plant may express themselves differently depending on how they are cultivated. For example, a clone brought up in an indoor growing facility may produce different morphology and chemotype levels than one grown outside. Similarly, identical twins may not be perfectly identical: one may be born with a mole on their cheek, or they may develop different physiologies if they grow up in different environments or have different eating and exercise habits. Thus, even the exact same genotype can produce different phenotypes.

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