Genetic Markers¶
Genetic markers are variant sites in the genome that can be detected, and they are the technical foundation of DNA testing and parentage verification. Understanding the types and uses of genetic markers is the prerequisite for reading a DNA test report.
Plain-language explanation (an analogy)¶
A genetic marker is like an individual "mark" in the "code book" of DNA:
- SNP (single-base variant) = one character in the book written as a different character, and the main basis for "performance talent" testing;
- STR (repeat sequence) = one sentence in the book copied a different number of times, like a "barcode", used for parentage verification and a DNA identity card.
Testing does not require reading the whole book — comparing a few key "marks" is enough.
Types of genetic marker¶
| Type | English | Description | Application |
|---|---|---|---|
| STR microsatellite | Short Tandem Repeat | Short sequences of 2-6 bases repeated in the genome, with the number of repeats highly variable between individuals | DNA identity card, parentage verification |
| SNP single nucleotide polymorphism | Single Nucleotide Polymorphism | Variation at a single base in the genome, an important genetic basis of trait differences | Flight ability gene testing |
| VNTR variable number tandem repeat | Variable Number Tandem Repeat | Variable-number tandem repeats of longer repeat units | Individual identification, parentage analysis |
| InDel insertion/deletion | Insertion/Deletion | Small-fragment insertion or deletion variants in the genome | Genotyping |
Comparison of the two core markers¶
| Dimension | SNP | STR |
|---|---|---|
| Form of variation | Single-base difference | Difference in repeat number |
| Main use | Performance genotyping | Parentage verification, DNA identity card |
| Power to distinguish individuals | Medium | High (like a barcode) |
Genotyping workflow¶
- DNA extraction: extract genomic DNA from samples such as feathers or blood cards;
- Marker amplification: amplify the target marker loci by PCR;
- Typing: obtain genotypes by electrophoresis, sequencing or fluorescence detection;
- Data interpretation: read the genotypes against a reference database.
Key points¶
- A genetic marker is a detectable variant site in DNA;
- SNP is used for performance gene testing, STR for parentage verification and DNA identity cards;
- Genotyping follows four steps: "extraction → amplification → detection → interpretation";
- Genetic markers are the technical foundation of DNA testing and parentage verification.