American Staffordshire Terrier
11 American Staffordshire Terriers in the atlas. Every number on this page has a source.
11 American Staffordshire Terriers in the Sniff Atlas. Population-genetic snapshot, Mendelian carrier frequencies from Donner 2023, and the data substrate's release version, sample sizes, and evidence tier on every claim.
In the atlas, the American Staffordshire Terrier clusters consistently as American Staffordshire Terrier (100% of the 11 dogs here).
Only 11 dogs of this breed in the atlas, modestly sampled.
Closest genetic neighbors in the atlas: Bulldog, Irish Terrier, Rhodesian Ridgeback, Toy Fox Terrier, and American Hairless Terrier.
What the genome says about American Staffordshire Terrier
Computed from the 18,477 research dogs in the Atlas.
- Bulldog16.66
- Irish Terrier17.83
- Rhodesian Ridgeback19.05
- Toy Fox Terrier19.57
- American Hairless Terrier20.39
Frequency of the alternate allele in this breed at each locus's representative SNP.
| IGF1 | 55% |
| HMGA2 | 68% |
| SMAD2 | 86% |
| LCORL | 96% |
| STC2 | 50% |
| ADAMTS17 | 50% |
| FGF4·CFA18 | 73% |
| FGF4·CFA12 | 86% |
| RSPO2 | 56% |
| FGF5 | 59% |
| KRT71 | 100% |
| MC1R | 77% |
| MSRB3 | 56% |
| BMP3 | 55% |
| SMOC2 | 68% |
What does the genome say about how a American Staffordshire Terrier looks?
American Staffordshire Terriers look the way they do because of a small set of fixed and near-fixed morphology genes that, taken together, define the visible breed. Each translation below pairs the gene with the trait an owner actually sees, the breed's allele frequency at that locus, and a one-clause causal phrase.
Size and build
IGF1 sits at 55% for the small-body allele. IGF1 is the gene that sets dog body size from Chihuahua to Great Dane. Intermediate frequencies typically keep a breed in the mid-sized range rather than tipping toward the larger working forms.
HMGA2 sits at 68%. HMGA2 is a chromosome-10 size locus that acts together with IGF1, and intermediate frequencies reflect partial commitment to the dominant size variant.
SMAD2 is near-fixed at 86%, a chromosome-7 height locus differentiating small from giant breeds.
LCORL is near-fixed at 96%, the NCAPG/LCORL height locus that is one of the strongest single contributors to canine body size.
STC2 sits at 50%.
ADAMTS17 sits at 50%. ADAMTS17 is a body-size locus also linked to lens disorders.
Leg length
The FGF4 retrogene on chromosome 18 sits at 73%. This is the leg-length variant. The intermediate frequency means some dogs in this breed carry the short-legged allele and some do not.
The FGF4 retrogene on chromosome 12 is near-fixed at 86%, the chondrodystrophic variant associated with intervertebral disc disease risk in breeds that carry it.
Coat type, length, and color
RSPO2 sits at 56% for the furnishings variant. Furnishings (the eyebrow-and-mustache pattern seen in Schnauzers and Wheaten Terriers) vary across the population at this intermediate frequency, and visible expression depends on the specific allele combination each dog carries.
FGF5 sits at 59% for the long-coat variant. Coat length is influenced by other loci as well, so intermediate FGF5 frequencies do not always correspond to intermediate visible coat lengths.
KRT71 is near-fixed at 100% for the wavy/curly variant. Coat curl phenotype varies across breeds at this fixation depending on modifier loci, and visible expression is not always curled even when the locus is fixed.
MC1R sits at 77% at the representative SNP. MC1R controls the switch between red-to-gold pigment and black-to-brown pigment, with the e/e homozygous genotype producing the gold-to-red spectrum. Substrate frequencies at this SNP depend on the array's polarity, so visible coat color in the breed is a more reliable indicator than this single number.
Ears
MSRB3 sits at 56% for the drop-ear allele, which is why ear set varies across the breed.
Skull shape
BMP3 sits at 55%, contributing to the breed's moderate, mesaticephalic head shape rather than the extreme brachycephalic form.
SMOC2 sits at 68%, contributing to the breed's moderate head shape.
What genetic diseases do American Staffordshire Terriers carry?
From a panel of 250 Mendelian-disease variants screened in 1,054,293 dogs (Donner et al. 2023), American Staffordshire Terriers carry 71 of them at observable frequency. Carrier frequency is not clinical risk. Most recessive variants require two copies for disease expression; many dominant variants show incomplete penetrance. Read this as a population fingerprint of what's in the gene pool, not a per-dog prediction.
Where every number on this page came from.
This page draws on three primary data sources. Carrier frequencies for the Mendelian section come from Donner et al. 2023 (CC-BY-4.0). We grade these data at evidence Limited because the cohort is a direct-to-consumer ascertainment, which biases toward owners who chose to test their dogs. The panel also uses tag-SNP proxies for some variants rather than direct causal-variant assays. Limited is a study-design grade, not a quality grade: the Donner cohort is the largest open canine-genotype dataset in existence and we are grateful for it. We rate the confounding MEDIUM.
Population-genetic dimensions (heterozygosity, intra-breed PCA distance, nearest neighbors, trait-locus frequencies) come from CanVAS (Brundage 2026), harmonized through the Sniff Atlas. The exact release date and verification commit are pinned at the bottom of the page so a researcher can trace a number back to a specific snapshot. The disease-gene-variant graph comes from OMIA (Online Mendelian Inheritance in Animals; Nicholas, Tammen, and the Sydney Informatics Hub at the Sydney School of Veterinary Science, The University of Sydney; retrieved April 2026, DOI 10.25910/2AMR-PV70).
What this page does not yet have. Inheritance modes and per-disease penetrance evidence from Donner 2023 are now in the structured data for every variant the panel covers. Mondo, OMIM, Ensembl, and HGNC cross-references on gene pages remain pending — they arrive in December 2026 alongside the imputed 9.67M-variant CanVAS dataset via the OMIA SQL dump absorption. Until then, gene IDs carry NCBI Gene and OMIA phene URLs only; the wider human-homolog and disease-ontology cross-reference set fills in with that release.
How to cite this page. The computed dimensions on this page are derived from the open Sniff Atlas v1.0.1 (Gehring 2026, doi:10.5281/zenodo.20566358, CC-BY 4.0). Full citation formats including BibTeX, RIS, and CITATION.cff at sniff.world/cite.
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- Donner J, Anderson H, Davison S, et al. (2023). Frequency and distribution of 152 genetic disease variants in over 1,000,000 mixed-breed and purebred dogs. PLOS Genetics 19(2):e1010651. doi:10.1371/journal.pgen.1010651
- Brundage J, et al. (2026). CanVAS: a harmonized canine variant atlas. bioRxiv. doi:10.64898/2026.04.13.718238
- Nicholas, F.W., Tammen, I., & Sydney Informatics Hub. (2026). Online Mendelian Inheritance in Animals (OMIA) [dataset]. The University of Sydney. https://omia.org. doi:10.25910/2AMR-PV70 (retrieved April 2026).