Long Coat vs Short Coat: The Long-Hair Gene in Dogs
Why two short-haired dogs can have a fluffy, long-haired puppy: the FGF5 gene, how long coats are inherited, the several long-hair variants researchers have found, and what a DNA test shows.
By PuppyGenes · How we research and write our guides
A long coat in dogs usually comes from the FGF5 gene. The long-hair versions are recessive, so a dog needs two copies to grow a long coat, and a short-haired dog can carry one copy without showing it. That's how two short-haired parents can have a long-haired, "fluffy" puppy. Researchers have found several different long-hair variants of FGF5, and a second gene, MC5R, helps explain the difference between short and medium coats.
The short version
- One main gene: FGF5, which normally limits how long hair grows.
- Recessive: a dog needs two long-hair copies to grow a long coat.
- Hidden carriers: short-haired dogs can carry one copy and pass it on.
- Several variants: more than one long-hair variant of FGF5 exists, and two different ones together also give a long coat.
- Short is the original: short-haired breeds carry the original versions of the main coat genes, like wolves.
- A second gene, MC5R, helps separate short coats from medium ones.
The long-hair gene: FGF5
FGF5 makes a growth factor involved in ending each hair's growth phase. Long-hair variants disrupt it, so hair grows longer, and the same gene affects hair length in mice and cats. A study of more than 1,000 dogs from 80 breeds found that a variant in FGF5 is one of three gene changes that together explain most coat types in purebred dogs. An earlier study had already linked FGF5 to the unusually long, "fluffy" coat that turns up in some Welsh Corgis.
The same study found that short-haired breeds carry the original versions of all three main coat genes, and that none of the coat variants turned up in the grey wolves it tested. A short coat is the starting point; a long coat is the newer trait.
How long coats are inherited
Because the long-hair versions are recessive, it takes a copy from each parent:
| Parents | Chance each puppy has a long coat |
|---|---|
| Two long-coated parents | Every puppy |
| A long-coated parent and a short-coated carrier | About 1 in 2 |
| Two short-coated carriers | About 1 in 4 |
| A parent with no long-hair copies | None |
That last row matters: if either parent carries no long-hair copies, no puppy can have a long coat from FGF5, however long the other parent's coat is.
More than one long-hair variant
The first FGF5 variant didn't explain every long-coated breed. Three very long-haired breeds in the 2009 study, including the Afghan Hound, didn't carry it. A 2013 study sequenced the whole gene and found several more long-hair variants:
- one that matched long hair in Akitas, and probably in long-coated Siberian Huskies;
- two new ones that, together with the original, explained long hair in every Afghan Hound studied;
- a different one in a long-haired Eurasier.
Samoyeds carried either two copies of one variant or one copy each of two different variants. All of the long-hair variants were recessive, and two different ones together still gave a long coat. That's why a DNA test that only looks for one variant can miss long hair in some breeds.
Short, medium and long: a second gene
FGF5 isn't the whole story. A 2016 study of more than 4,200 dogs found a second gene, MC5R, linked to coat length. Shorter-haired breeds such as the Bull Terrier and the Greyhound carry a different version of MC5R from medium-haired breeds such as the Akita and the Pembroke Welsh Corgi. Long-haired breeds such as the Maltese and the Old English Sheepdog carry two copies of a long-hair FGF5 variant.
Coat length also changes how other coat genes look. With furnishings, a short coat looks wiry and a long coat looks soft and shaggy, and coat length also changes how visible curl is. Our guides to furnishings and curly coats explain those genes.
Long coats in daily life
A long coat needs more brushing to stay free of tangles, and how much it sheds depends on other genes, especially furnishings and whether the dog has a dense undercoat. Our guide to the genetics of shedding covers both. In a Canadian winter, a long, thick coat can help, but it collects snow and ice too; our guide to the best dogs for Canadian winters covers how coat type affects cold tolerance.
How a DNA report shows coat length
The PuppyGenes physical appearance section includes a coat length prediction based on FGF5, with its own confidence. In our public example reports, both Juno and Marley are predicted to have a "likely long coat", at low confidence. Treat a low-confidence prediction as tentative, and trust the coat you can see.
Frequently asked questions
- Can two short-haired dogs have a long-haired puppy?
- Yes, if both parents carry one hidden copy of a long-hair FGF5 variant. On average, about one puppy in four from two carriers will have a long coat. If either parent carries no long-hair copies, none of the puppies will.
- Why is my French Bulldog fluffy?
- A long, fluffy coat in a normally short-coated breed usually means the dog inherited two recessive long-hair copies of FGF5, one from each short-haired parent, as researchers described in "fluffy" Welsh Corgis. A DNA test that covers coat length can show whether that's what happened in your dog.
- What gene causes long hair in dogs?
- Mostly FGF5. Several long-hair variants of FGF5 have been found, and they're all recessive. A second gene, MC5R, helps separate short coats from medium ones.
- Is long hair dominant or recessive in dogs?
- Recessive. A dog needs two long-hair copies of FGF5, one from each parent, to grow a long coat. Dogs with one copy usually have short coats but can pass the long-hair copy on.
- Can a DNA test tell if my puppy will have a long coat?
- It can predict coat length from FGF5. The PuppyGenes physical appearance section includes a coat length prediction with its own confidence. Because there are several long-hair variants, the confidence shown with each result matters.
From general to personal
See how this applies to your dog specifically.
Our at-home Complete Dog DNA Test adds your dog's own results to these tips across six report sections: breed ancestry, coat colour, physical appearance, temperament and size predictions, genetic diversity and oral microbiome. The report does not include genetic disease or health screening.