DNA profiling in dogs has emerged as an essential tool for breed identification, parentage verification, and understanding genetic health markers. The main applications and features of DNA genetic profiling include the following:
1. uniquely identify the animal
2. does not change during life
3. an animal without or with a non-functioning microchip can be identified
4. verification of parentage (paternity, maternity)
5. verification of “clear” after parents
Two prevalent methodologies have emerged in the recent past: the ISAG 2006 which utilizes short tandem repeats (STRs) and the more recent ISAG 2020 which employs single nucleotide polymorphisms (SNPs). This article provides a brief comparison between the two and elucidates why the newer ISAG 2020 method has become increasingly favored.
ISAG 2006: STR-Based Profiling
The ISAG 2006 DNA profiling method uses approximately 21 STR markers. STRs, or short tandem repeats, are short sequences of DNA that are repeated in a head-to-tail manner. They have been used in various genetic applications, including:
- Animal identification: DNA profile serves as a unique DNA fingerprint for each animal
- Parentage Verification: STRs are highly polymorphic, which enables confirmation of paternity or maternity
Limitations of ISAG 2006:
- Limited Genetic Information: With only 21 STR markers, there’s a limited scope for comprehensive genetic analysis.
- Parentage Verification Limitation: In some cases, a maternal DNA profile is also required to establish paternity.
ISAG 2020: SNP-Based Profiling
The ISAG 2020 method involves the assessment of around 220 SNP markers. SNPs, or single nucleotide polymorphisms, are individual points in the DNA where variations can occur. They offer a multitude of advantages for genetic profiling:
- Higher Resolution: Given the larger number of markers, SNPs provide a more in-depth genetic profile.
- More Stable: SNPs are generally more stable than STRs, resulting in fewer mutations and thus more consistent results.
- Broad Application: SNPs can be used for parentage, breed identification, sibling verification, heterozygosity estimation.
Advantages of ISAG 2020:
- Comprehensive Analysis: With ten times more markers, ISAG 2020 offers a broader genetic insight.
- More Accurate: The stability of SNPs ensures a higher accuracy rate.
- Future-Proof: As the field of genomics advances, having a dense array of markers ensures the method remains relevant for various applications.
- More advanced analysis features: ISAG 2020 allows heterozygosity assessment, sibling confirmation and may allow other relationship confirmation (e.g. grandmother – grandson).
| Analysis | ISAG 2006 | ISAG 2020 |
| Animal identification | ✔ | ✔✔ |
| Maternity verification | ✔ | ✔ |
| Paternity verification | ✔ | ✔ |
| Heterozygosity | ✘ | ✔ |
| Sibling verification | ✘ | ✔ |
| Estimation of heterozygosity in the litter | ✘ | ✔ |
| Population genetics, diversity | ✘ | ✔ |
While the ISAG 2006 method has served the dog breeding and genetics community well, the ISAG 2020 emerges as a more comprehensive and future-proof methodology. The richness of data provided by the 220 SNP markers, combined with their stability and broad applicability, makes the ISAG 2020 method preferable for those seeking the most accurate and in-depth genetic insights into their dogs.
It is expected that ISAG 2020 will become the standard for canine DNA profiling in the near future.
As ISAG 2006 and 2020 are not compatible, breeders cannot compare their ISAG 2006 and 2020 reports.
For the reasons given above, it is recommended that breeders use the newer ISAG 2020 DNA profile test.
