Genetic Identity Testing and Marker Systems
Select and validate marker systems for the identity question, biological unit, reference set, and error tolerance.
Educational reference · evidence, sources, and limits shown below
Select and validate marker systems for the identity question, biological unit, reference set, and error tolerance.
Terms to know
- SSR
- Short tandem repeat locus genotyped by fragment length; also called a microsatellite.
- SNP
- Single-nucleotide polymorphism used individually or in panels.
- GBS
- Reduced-representation sequencing used to discover and genotype many markers.
- Fingerprint
- Multilocus profile compared with a declared reference and matching rule.
Core science
Identity testing is comparative. A marker panel can show that two samples match within its resolution, differ, or have an estimated relationship; it cannot authenticate a name without a verified reference tied to that name. The same panel may be suitable for clone matching but weak for parentage, population ancestry, or trait prediction.
SSRs are economical and informative but can suffer allele-calling differences between laboratories. SNP panels are scalable but depend on marker selection and reference populations. GBS and whole-genome sequencing provide more loci while adding missing data, mapping, batch, and bioinformatic choices.
A defensible fingerprint system uses reference plants, duplicate tissue samples, chain of custody, positive and negative controls, replicate thresholds, and predefined match metrics. Closely related siblings can be difficult to distinguish with small panels, while somatic mosaicism can produce low-level differences within a clone.
Why this matters in cultivation
- Create a controlled reference sample at intake before plants are multiplied or distributed. A later sample labeled by reputation cannot retroactively authenticate earlier inventory.
- Use identity, sex, and chemotype markers as separate modules. A plant can match a clone fingerprint while failing chemistry due to environment or sampling.
Measure and record
Question
Clone match, parentage, duplicate detection, population assignment, sex, chemotype, or trait marker.
Reference set
Verified samples, source documents, duplicates, custody, storage, and version.
Panel
Loci, coordinates, allele definitions, platform, missingness, error rate, and resolution study.
Comparison
Similarity metric, mismatch threshold, relatedness model, confidence, and ambiguous class.
Governance
Database access, reanalysis rules, naming authority, conflict handling, and retention.
Common misconceptions
Correction: Only a verified reference can connect the profile to a controlled name.
Correction: Sample mix-up, reference error, contamination, and analysis choices remain.
Correction: Association with a trait and uniqueness of an individual are different requirements.
Evidence limits
Marker performance depends on allele frequencies and relatedness in the tested population. Proprietary panels without disclosed validation, references, or match rules cannot support independently auditable claims.
Related encyclopedia topics
- THC-ENC-022, THC-ENC-148-153, THC-ENC-159-160, THC-ENC-161-180, and THC-GROW-030.
Source notes
- Henry P. et al. (2020). A single nucleotide polymorphism assay sheds light on cannabis population structure and genetic relatedness. Journal of Cannabis Research 2:26.
- Borin M. et al. (2021). Developing and testing molecular markers in Cannabis sativa for sex and chemotype. Plants 10:2109.
- Schwabe A.L. and McGlaughlin M.E. (2019). Genetic tools weed out misconceptions of strain reliability in Cannabis sativa. Journal of Cannabis Research 1:3.
- Cascini F. et al. (2019). Highly predictive genetic markers distinguish drug-type from fiber-type Cannabis sativa L. Plants 8:496.
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.