Is it possible for animals to have Down syndrome? All animals – human beings included – are susceptible to genetic disorders and different diseases.
As of now, there have been no confirmed cases of Down syndrome in any mammal other than human beings. While we have all seen the adorable pictures of animals implying that they have Down syndrome, their unique look is usually do to other genetic factors.
In this article, we take a deep dive into the subject of animals with Down syndrome, and explore similar genetic mutations and disorders.
What is Down Syndrome?
In order to analyze whether or not animals really can have Down syndrome, it’s necessary to detail exactly what this genetic disorder really is.
Down syndrome is a common genetic disorder caused by abnormal cell division that results in an extra full or partial copy of chromosome 21. All genetic information of human beings is found within our chromosomes. They are molecular structures formed by DNA, normally found in 23 pairs.
Known by medical professionals as Trisomy 21, Down syndrome is not a disease, but rather a genetic disorder. It’s estimated to occur in about 1 in every 700 babies. Cases of Down syndrome can be found in children born to parents with completely normal genetic structures, making it nearly impossible to predict through genetic testing before pregnancy.
While it is both a common and manageable disorder, down syndrome can present a number of physical and mental challenges for diagnosed individuals.
Are there Animals with Down Syndrome?
There are a variety of disorders and diseases that human beings share with animals, but Down syndrome has yet to be confirmed as one of them. While animals can sometimes have the same symptoms as those found with Down syndrome, they are usually do to other genetic abnormalities most often caused by issues with breeding.
With that being said, there have been recorded cases of primates having chromosomal abnormalities that very much resemble human down syndrome. In chimpanzees, the 22nd chromosome is akin to the human chromosome 21. Scientists have documented the occurrence of an extra copy of chromosome 22 in chimps as Trisomy 22, labeled “quasi down syndrome” by many media outlets. In such cases, symptoms were recorded that closely resemble those of human down syndrome, such as vision problems, growth retardation, facial deformations, cognitive impairment, heart problems, and more. (source)
Explanation for “Animals with Down Syndrome”
Since there are no other animals with the same exact genetic sequencing of human beings, it’s impossible to diagnose any animal with Down syndrome disorder in particular. There are however, many different disorders and diseases found in animals that can result in similar symptoms to that of Down syndrome.
Breeding Practices of White Tigers
There is no shortage of images and videos on the internet showing supposed animals with Down syndrome. Perhaps the most popular are that of Kenny the tiger. While he does not have Down syndrome disorder, Kenny does have facial deformities, alongside a number of other health complications.
In Kenny’s case, the physical abnormalities are due to a long line of aggressive inbreeding. Being breed and raised in captivity, Kenny was not only subject to inbreeding, but also poor living conditions highlighted by cages littered with feces and the remains of dead chickens. It’s estimated his living conditions also contributed to additional health complications. (source)
Of all the animals in the animal kingdom, the white tiger is perhaps the most prone to physical deformations and disorders. Because they are so rare in nature, yet highly desired for their beautiful fur, white tigers have long been subject to aggressive breeding programs.
Scientifically speaking, white tigers are not a “species.” The appealing color of the white tigers coat happened by chance of genetics. The typical orange tiger we are all familiar with can produce offspring with varying shades of white to orange, just as the American black bear can be found with black, brown, tan, and cinnamon colored coats.
Considering this, there is only one way breeders can achieve the double-recessive gene combination that results in the signature fur of the white tiger – by breeding tigers over and over again until that specific gene combination presents itself. Of course, the best chance of ensuring a white coat is by breeding two white tigers together. In the case of Kenny, his parents were direct siblings forced to breed together on multiple occasions. Kenny’s brother, an orange tiger, was born cross-eyed.
Can Dogs and Cats have Down Syndrome?
Dogs, cats, and people have many similarities. It’s why we all get along so well! But, when I comes to Down syndrome, because dogs have 39 sets of chromosomes, and we have 23, it’s impossible to make the diagnosis. Because of the differences in genetic structure, if a dog were to have an extra chromosome 21, it would result in an entirely different genetic condition than that of Down syndrome. (source)
Not all animals have upwards of 21 pairs of chromosomes, cat’s included, making the feline species devoid of the 21st chromosome present in humans. While an extra chromosome may not cause Down syndrome in cats, they can still have other genetic mutations and conditions that share similar symptoms.
Perhaps the most intriguing internet-sensation when it comes to “cats with Down syndrome,” was the kitten, Otto. While his condition later resulted in an early death due to heart failure – a common effect of Down syndrome – Otto was actually the only cat ever diagnosed with Down syndrome by a veterinarian.
Otto was diagnosed on the basis of the shape of his face and abnormal forehead structure by a veterinarian in Turkey. However the condition was never verified, as Otto died before blood tests on chromosomal structure could be completed.
While dogs and cats may not have Down syndrome specifically, they can be impacted by many genetic mutations and various health conditions. A few of the most common, that also share symptoms with Down syndrome, include the following:
- Hormone deficiency
- Feline dwarfism
- Pituitary dwarfism
- Skeletal dysplasia
- Congenital hypothyroidism
- Portosystemic shunt
- Aggressive bone infection
A few of the common symptoms shared between the above-mentioned conditions and Down syndrome include slow growth resulting in small stature, large tongue, shorter limbs, cognitive delay, poor muscle tone, and many others.
A Look at Genetic Conditions in Primates – Down Syndrome Research
As we mentioned earlier in the article, apes can have a genetic mutation resulting from an extra chromosome that gives them the appearance of having Down syndrome. Because apes are so closely related to human beings, it seems more conceivable that a primate could be actually diagnosed with the condition. Gorillas are said to have a DNA sequence that’s similar to humans by a factor of around 98%. (source)
Apes have 24 pairs of chromosomes in comparison to our 23. In human beings, Down syndrome occurs when an extra copy of chromosome 21 is present. In primates, the closest diagnosis – Trisomy 22 – is a result of an additional chromosome 22.
A chimp named Kanako was the most recent primate to be diagnosed with Trisomy 22. She experienced symptoms of stunted growth, congenital heart disease, underdeveloped teeth, and partial blindness. All of her symptoms, even the aggressive cataracts in her eyes, align with symptoms of Down syndrome.
Thus far, there has only been one other primate every diagnosed with Trisomy 22. Although, research in Tanzania may be producing more cases of the genetic mutation. Scientists hope that with the closely related genetic structure of chimps, future cases of Trisomy 22 will be able to help us better understand Down syndrome and related conditions. (source)
Laboratory Mice Modeling Down Syndrome
Mouse models have long been used by scientists to study diseases and disorders also found in human beings. In July of 2020, scientists at the Johns Hopkins University, School of Medicine were able to create a mouse replica of Down syndrome for the first time.
Within the 21st chromosome, there are more than 500 genes that can be overexpressed, such as the genetic facial deformities and cognitive difficulties we often associate with Down syndrome. This makes it a complex and diverse disorder to study in comparison to similar genetic conditions.
Researchers in the Johns Hopkins laboratory were able to insert a copy of the human chromosome 21 into lab mice, using the rodent’s own specific cellular structure and organized DNA. This enables the mice to develop with the condition, just as a human being might develop with the condition over time.
The mice, named TcMAC21 by researchers, share common symptoms with individuals who have down syndrome, most notably the distinct facial structure, congenital heart defects, and cognitive difficulties resulting from a smaller cerebellum. For researchers in the medical field, this is a huge step in gaining a better understanding of how we might be able to better treat Down syndrome in the future. (source)
Conclusion on Animals with Down Syndrome
Can animals really have down syndrome? No, animals can not technically have the same diagnosis as Down syndrome because of the variations in chromosomal structure. However, it is possible for an animal to have a chromosome abnormality that closely resembles that of Down syndrome.
The mental disabilities and physical deformations seen in animals portrayed to have Down syndrome are usually a result of these other chromosome abnormalities. It’s difficult to say whether or not scientists will be able to complete the chromosomal testing necessary to confirm a case of Down syndrome in animals. As for now, Down syndrome is only a condition present in human beings.