Diploidy, Meiosis, and Genetic Recombination
Trace chromosome segregation and recombination from a diploid parent to genetically variable haploid gametes and offspring.
Educational reference · evidence, sources, and limits shown below
Trace chromosome segregation and recombination from a diploid parent to genetically variable haploid gametes and offspring.
Terms to know
- Diploid
- Having two homologous chromosome sets in the ordinary sporophyte generation.
- Meiosis
- Two successive divisions that reduce chromosome number and generate haploid spores leading to gametes.
- Recombination
- Exchange or reassortment that creates new combinations of parental alleles.
- Linkage
- Tendency of nearby loci on the same chromosome to be inherited together.
Core science
A typical diploid cannabis plant forms haploid reproductive cells through meiosis. Homologous chromosomes pair, exchange segments through crossing over, and segregate; sister chromatids then separate. Fertilization restores diploidy. The result is not a shuffled copy of a whole parent but a new combination of chromosome segments from both parents.
Independent assortment applies most cleanly to loci on different chromosomes or far apart. Linked loci can travel together, while recombination frequency depends on physical position, chromosome structure, sex, and the cross. Suppressed recombination around differentiated sex-chromosome regions and rearranged cannabinoid-synthase regions can make simple probability assumptions fail.
A cutting bypasses meiosis and preserves the sampled plant’s nuclear genotype far more closely than seed reproduction. Selfing, sibling mating, backcrossing, and outcrossing all pass through meiosis and expose different combinations, homozygosity, linkage blocks, and recessive variation.
Why this matters in cultivation
- A breeding record must identify both parents, their sex-expression method, plant IDs, direction of the cross, pollen isolation, seed family, and generation. A cultivar name alone cannot reconstruct the recombination event.
- Observed segregation should be compared with a stated genetic hypothesis, adequate progeny count, and the possibility of linkage, selection, pollen contamination, mislabeling, or scoring error.
Measure and record
Cross identity
Female and pollen parents, clone or line IDs, direction, dates, isolation, and operator.
Generation
F1, F2, backcross, selfed family, open-pollinated family, or other defined relationship.
Population
Seeds produced, plants germinated, plants scored, exclusions, deaths, and missing observations.
Markers
Loci, phase if known, parental calls, progeny calls, recombination estimate, and quality filters.
Deviations
Unexpected classes, suspected contamination, selection before scoring, and corrective action.
Common misconceptions
Correction: Offspring receive chromosome segments, not equal halves of visible traits.
Correction: Nearby loci may remain associated unless recombination separates them.
Correction: Selfing includes meiosis and produces segregating offspring unless the parent is fully homozygous.
Evidence limits
Recombination landscapes are not equally resolved across cannabis genomes, populations, and sexes. Small families provide unstable segregation and linkage estimates, especially for rare classes.
Related encyclopedia topics
- THC-ENC-018, THC-ENC-021, THC-ENC-141, THC-ENC-143-145, and THC-ENC-181-200.
Source notes
- Laverty K.U. et al. (2019). A physical and genetic map of Cannabis sativa identifies extensive rearrangements at the THC/CBD acid synthase loci. Genome Research 29:146-156.
- Prentout D. et al. (2020). RNA-seq segregation analysis identifies the sex chromosomes of Cannabis sativa. Genome Research 30:164-172.
- Woods P. et al. (2021). Quantitative trait loci controlling agronomic and biochemical traits in Cannabis sativa. Genetics 219:iyab099.
- THC Cannabis Plant Science Source Packet v1.1 (project source, May 2026).
This lesson summarizes the source material and its evidence limits for education. Use direct measurement, controlled comparison, and the cited sources when conditions differ or a decision carries meaningful risk.