# Segregation

> Segregation is the separation of a plant's two alleles at each locus into different gametes, so offspring of a heterozygous parent vary in which allele they get.

- Canonical: https://genetixbay.com/knowledge/glossary/segregation.html
- Also written: Mendelian segregation, law of segregation, segregating, segregates
- 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"

Segregation is Mendel's first law: the two [alleles](https://genetixbay.com/knowledge/glossary/allele.md) a plant carries at a locus separate during meiosis, and each pollen grain or ovule receives only one of them. Offspring of a [heterozygous](https://genetixbay.com/knowledge/glossary/heterozygous.md) parent therefore differ in which allele they inherit.

## In practice

Breeders say a line "is still segregating" when its seedlings vary for a trait. That is normal in [F2](https://genetixbay.com/knowledge/glossary/f2.md) and later generations from a cross, and in [S1s](https://genetixbay.com/knowledge/glossary/s1.md) from a heterozygous clone. The F2 is where segregation is widest: traits hidden in a uniform [F1](https://genetixbay.com/knowledge/glossary/f1.md) reappear, and new combinations show up. That spread is what makes the F2 the classic generation for hunting.

[Stabilising](https://genetixbay.com/knowledge/glossary/stabilisation.md) a line means selecting until segregation stops for the traits you care about: the plants become [homozygous](https://genetixbay.com/knowledge/glossary/homozygous.md) there and breed true. Segregation for traits you did not select on carries on quietly.

## Don't confuse with

- **Independent assortment**: about how different genes combine; segregation is about the two alleles of one gene.
- **Mutation or drift**: segregation reshuffles alleles that already exist; it creates no new ones.
- **Herms in a seed line**: these reflect the line's genetics and breeding history, not segregation of one simple gene.

## Related terms

[Mendelian inheritance](https://genetixbay.com/knowledge/glossary/mendelian-inheritance.md), [Independent assortment](https://genetixbay.com/knowledge/glossary/independent-assortment.md), [F2](https://genetixbay.com/knowledge/glossary/f2.md), [Heterozygous](https://genetixbay.com/knowledge/glossary/heterozygous.md), [True breeding](https://genetixbay.com/knowledge/glossary/true-breeding.md)

## Read more

- [F1, F2, F3 explained: what filial generations really mean](https://genetixbay.com/knowledge/breeding/f1-f2-f3-explained.md)
- [Mendelian genetics for growers, with Punnett squares](https://genetixbay.com/knowledge/breeding/mendelian-genetics-for-growers.md)

## Sources

1. Miko I. 2008. Gregor Mendel and the principles of inheritance. Nature Education 1(1):134. https://www.nature.com/scitable/topicpage/gregor-mendel-and-the-principles-of-inheritance-593/
2. Allard RW. 1999. Principles of Plant Breeding, 2nd edition. John Wiley & Sons, New York. ISBN 978-0-471-02309-0