Alice White
Time and again, photos of dogs with unusual facial features are circulating on the Internet, suggesting a genetic defect such as Down syndrome. But it is not that simple. We clarify whether dogs can get trisomy 21 at all and what the allegedly affected animals are all about.
What is Down Syndrome?
Down syndrome or trisomy 21 is a genetic defect in humans. In the affected persons, chromosome 21 is present threefold instead of a double variant. The additional chromosome leads to mental and physical undesirable development.
The genetic disorder leads to cognitive limitations and characteristic external features such as a flat face with narrow eyes. Down syndrome occurs relatively frequently in humans: around one in 800 people is affected by the genetic defect on the 21st pair of chromosomes.
Can Dogs Have Down Syndrome?
Although it looks like this in some photos on the Internet, Down syndrome does not exist in dogs. Trisomy 21 is a genetic defect that has so far only been found in humans and other primates with human-like DNA.
A similar mutation was found in chimpanzees, which affects the 22nd chromosome pair of the animals. Although a different pair of chromosomes are affected, the physical and mental symptoms of affected chimpanzees are similar to those of human Down syndrome.
This mutation does not occur in dogs.
Pictures of cats with Down syndrome are also often circulating on the internet, but this is also misinformation.
Are There Similar Genetic Defects in Dogs?
Dogs do not have Down syndrome, but they can have other genetic mutations. The symptoms of gene mutations in dogs may appear similar to trisomy 21 at first glance. For example, dogs with a genetic defect have a deformed face or are more prone to disease.
A well-known example of a dog with a genetic defect is the Narwhal puppy, which has a tail growing in its face. The pictures of dogs and other animals such as lions or tigers, which allegedly have Down syndrome, that is disseminated on the Internet show animals with malformations, mutations, or genetic defects, which are not, however, trisomy 21.
How is the Dog’s DNA Structured?
The reason dogs don’t get Down syndrome is because of their DNA. Because the genetic building blocks of dogs differ fundamentally from those of humans. Dogs have 39 pairs of chromosomes, which corresponds to 78 individual chromosomes.
The 21st pair of chromosomes, the mutation of which causes trisomy 21 in humans, has a different function in dogs than in humans. If chromosome 21 is mutated in a dog’s embryo, it is very likely that the puppy will not be born alive, but will die in the womb or shortly after birth.
