Segregation is Mendel's first law: the two alleles a plant carries at a locus separate during meiosis, and each pollen grain or ovule receives only one of them. Offspring of a heterozygous 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 and later generations from a cross, and in S1s from a heterozygous clone. The F2 is where segregation is widest: traits hidden in a uniform F1 reappear, and new combinations show up. That spread is what makes the F2 the classic generation for hunting.
Stabilising a line means selecting until segregation stops for the traits you care about: the plants become homozygous 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.
An allele is one version of a gene; a diploid cannabis plant carries two alleles at each locus, one from each parent, which may be the same or different.A plant is heterozygous at a locus when it carries two different alleles there (Aa), so its offspring can inherit either one and segregate.F2 is the second filial generation, made by crossing or selfing F1 plants; it shows the widest segregation, bringing back hidden recessives and new combinations.S1 is seed from a plant pollinated with its own pollen; every S1 seed is female and a new genotype, not a copy of the parent.F1 is the first generation of offspring from crossing two parents; if the parents are inbred and different, F1 plants are uniform and often show hybrid vigour.Stabilisation is breeding a seed line over several generations, with selection each time, until it reliably reproduces the chosen traits from seed.A plant is homozygous at a locus when it carries two identical alleles there (AA or aa), so it passes the same allele to every offspring.Independent assortment is Mendel's rule that alleles of genes on different chromosomes are passed to gametes independently of each other, creating new trait combinations.Mendelian inheritance is the pattern in which single genes pass from parents to offspring in predictable ratios, following Mendel's laws of segregation and independent assortment.A true-breeding line produces offspring that consistently look like the parents for a given trait, because the plants are homozygous for the alleles behind it.
