Rat Terrier
Only 8 Rat Terriers have been tested for carrier variants (Donner 2023), too few to say what the breed carries. Only 9 dogs stand behind the atlas figures here, so little is known yet.
Also known as American Rat Terrier, Decker Giant, Rat, and Rat, Standard Terrier.
What genetic diseases do Rat Terriers carry?
From a panel of 250 Mendelian-disease variants screened in 1,054,293 dogs (Donner et al. 2023), Rat Terriers carry 2 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.
CATwhat this gene does
CAT is a gene that helps produce an enzyme called catalase, which breaks down hydrogen peroxide in the body to prevent cell damage.
For your dog: If your dog is from a breed that can carry this gene, it’s worth asking your vet about testing. Being a carrier doesn’t mean your dog is affected, but it can inform health decisions.
PRCDwhat this gene does
PRCD is a gene involved in the health of a dog's retina, the part of the eye that detects light and helps with vision.
For your dog: If your dog belongs to a breed known to carry PRCD changes, it's worth discussing eye health and potential genetic testing with your vet.
Other names
The Rat Terrier is also recorded as American Rat Terrier, Decker Giant, Rat, Rat, Standard Terrier, Rattie, Ratting Terrier, and RT.
Identified as Rat Terrier (VBO:0201125) in the Vertebrate Breed Ontology (Mullen et al. 2025, CC-BY 4.0) · registry IDs iDog 202 · VeNom 22635.
For researchers Population genetics, disease models and every recorded condition Open the research detail for the Rat Terrier
In the atlas, the Rat Terrier clusters consistently as Rat Terrier (100% of the 9 dogs here). Genetic diversity is high (mean heterozygosity 0.3807), reflecting either a mixed-breed cluster or breeds with broad genetic backgrounds.
Mean heterozygosity is 0.381, notably high, indicates broad genetic background. Only 9 dogs of this breed in the atlas, every individual contributes outsized weight to the breed's computed profile.
What the atlas genotypes say about Rat Terrier
Computed from the 14,478 CanVAS dogs in the Atlas, on an imputed genotype backbone: 77,215 directly typed sites per dog, imputed to 9.67 million variants.
The confidence below counts dogs, not reads: it is the size of the sample, and it is separate from how the genotypes were measured.
Not enough dogs in the atlas yet (n=9) for a reliable diversity figure. It fills in as more are added.
What does genetic diversity mean?
How varied a breed's gene pool is — the share of gene spots where a typical dog of the breed carries two different versions rather than two identical ones.
How to read it: Higher = more diverse. Among well-sampled breeds it ranges roughly 0.22 (least diverse) to 0.33 (most diverse).
Diversity is a strength, not a verdict on any individual dog. Lower diversity means it's worth paying attention to recessive-risk testing — not that a dog is doomed.
Not enough dogs in the atlas yet (n=9) to resolve cluster structure. It fills in as more are added.
What does within-breed variation mean?
How much individual dogs within the breed differ from each other genetically.
How to read it: Higher = more internal variety among individuals of the breed.
Sensitive to how many dogs of the breed we've sampled.
Rat Terriers are a natural model for human disease
Because the same genes cause the same conditions across species, the inherited conditions documented in Rat Terriers help researchers understand, and work toward treating, the human diseases they model. This is the dog advancing human medicine. The breed models the human disease; it does not have it, and this is not a prediction for your dog.
- amyotrophic lateral sclerosis type 1, modeled by the breed's Degenerative myelopathy via SOD1, the same underlying biology.
- thyroid dyshormonogenesis 2A, modeled by the breed's Hypothyroidism, congenital via TPO, the same underlying biology.
- Duchenne muscular dystrophy, modeled by the breed's Muscular dystrophy, Duchenne type via DMD, the same underlying biology.
- OMIM:607591, modeled by the breed's Hypotrichosis, recessive , the same underlying biology.
- Weill-Marchesani 4 syndrome, recessive, modeled by the breed's Lens luxation , the same underlying biology.
- methemoglobinemia due to deficiency of methemoglobin reductase, modeled by the breed's Methaemoglobinaemia, CYB5R3-related , the same underlying biology.
Every condition recorded in the Rat Terrier
Beyond the testable carriers above, OMIA's literature catalogue records 7 genetic conditions in the Rat Terrier, 7 of which have a known human equivalent. This is the documented landscape across all Rat Terriers ever studied, not a prediction for any one dog.
- Degenerative myelopathy Autosomal recessiveHuman equivalent: amyotrophic lateral sclerosis type 1
- Hypothyroidism, congenital Autosomal recessiveHuman equivalent: thyroid dyshormonogenesis 2A
- Muscular dystrophy, Duchenne type X-linked recessiveHuman equivalent: Duchenne muscular dystrophy
- Hypotrichosis, recessive Autosomal recessiveHuman equivalent: OMIM:607591
- Lens luxation Autosomal recessiveHuman equivalent: Weill-Marchesani 4 syndrome, recessive
- Methaemoglobinaemia, CYB5R3-related Autosomal recessiveHuman equivalent: methemoglobinemia due to deficiency of methemoglobin reductase
- Human equivalent: OMIM:602307
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 in the structured data for every variant the panel covers. Mondo, OMIM, Ensembl, and HGNC cross-references live on the gene and disease pages this page links to, rather than being repeated here. What is still absent from this breed page is anything not in the cited panel, and each such gap carries its cause where it appears.
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.
Some things about living with a rat terrier never make it into a database. Add what you know as a Keeper, in your words →
Lived experience, kept beside the science.We have 9 rat terriers. We do not have yours.
Every rat terrier added sharpens the breed's genetic neighborhood. Enrollment is free. The data stays open. The star is permanent.
- Donner J, Freyer J, Davison S, Anderson H, Blades M, Honkanen L, et al. (2023). Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs. PLOS Genetics 19(2):e1010651. doi:10.1371/journal.pgen.1010651
- Brundage DM (2026). CanVAS: A Harmonized and Imputed 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).