They may be lovely to look it, but it's now common knowledge that the features of some breeds of dog may not be so great for their health.
French bulldogs, English bulldogs, pugs and Boston terriers are among several types of dog with short, squashed noses. Many of these pooches end up suffering from a condition called Brachycephalic (pronounced brak-ee-suh-fal-ik) Obstructive Airway Syndrome, or BOAS.
This disease can lead to a number of health issues including problems with breathing and difficulties getting air into the lungs - as affected dogs have a narrower windpipe - and a lack of oxygen in the blood.
These types of breathing problems in flat-faced dog breeds have usually been blamed on their noses, but new research has revealed that genetics may have a big part to play.
What did the study involve?
A team based at the University of Edinburgh have published a study which looks at Norwich terriers. This breed of dog doesn't share the same flatter face that pugs and bulldogs have, but can suffer from a similar breathing problem called Upper Airway Syndrome (UAS).
For the study, researchers looked at genetic variations that could be linked to BOAS and UAS.
They examined the airways of over 400 Norwich terriers and carried out what is known as a genome-wide association study. This involves searching genomes - the microscopic bits of DNA that make animals what they are - for small differences which crop up more frequently in animals that have a particular disease compared to those without it.
What were the findings?
The team's findings revealed a mutation in a gene called ADAMTS3 which they also found in French and English bulldogs. In addition to this, they discovered that other studies in this area have linked mutations in the ADAMTS3 gene to an illness called edema. This illness is commonly found in the airways of Norwich terriers and bulldogs suffering from breathing problems.
Jeffrey Schoenebeck, who is one of the authors of the study, said: "We conclude that there are additional genetic risk factors, that if inherited, will likely lead to airway disease in dogs regardless of their face shape." So, whatever a dog's face looks like, they're DNA could be causing them problems with their breathing.
The researchers hope their findings will help to introduce better breeding practices to prevent the defective gene from being passed on. They also believe it could lead to treatments for certain breeds of dog that take lots of different health risks into consideration.