Down syndrome is a genetic abnormality in which chromosome 21 has three copies, instead of the usual two. Humans have 23 pairs of chromosomes, out of which pair no. 21 is affected in Down syndrome. In this chromosomal disorder, the cells get abnormally divided, resulting in formation of a third copy of chromosome 21. This triplication of chromosome 21 material results in intellectual disability―a prominent feature of Down syndrome.
Did You Know?Inbreeding of animals is one of the common causes of genetic disorders in their offspring.
People with this genetic disorder suffer from learning difficulties. They experience lack of problem solving and social reasoning skills. People with Down syndrome have characteristic facial features such as round face, prominent ears, flat nasal bridge, and upward slanting eyes. However, Down syndrome is not limited to humans, animals too can suffer from this genetic disorder. It is discussed below:
Can Animals Get Down Syndrome?
The closest relatives of us humans in the animal kingdom do share symptoms with mental illnesses like Down syndrome. Since humans have evolved from apes, it is observed that the genetic makeup of humans and chimpanzees is 99% similar. Humans have 46 chromosomes (23 pairs), while chimps show 48 chromosomes (24 pairs). This means, genetically, chimpanzees closely resemble humans. No wonder, chimpanzees suffer from a similar syndrome.
Dogs with Down Syndrome
It is rare to find cases of dogs with Down syndrome. Dogs have 78 chromosomes per cell, and any defect in chromosome 21 can actually be fatal for dogs. The chances of Down syndrome puppies surviving for long is pretty slim. This is because the developing fetus having such chromosomal abnormalities does not grow properly in the mother's womb.
- Observing a puppy with Down syndrome, one can easily notice its unusual physical features such as occurrence of skin patches, chronic dry nose, scanty hair and thinning coat due to frequent hair loss.
- Dogs suffering from this genetic condition tend to have congenital heart defects, poor vision, hearing problems, and thyroid disorders that often lead to fluctuations in body temperature.
- Cognitive disability can also be noticed as they find it difficult to grasp simple commands. Unusual movement and ambulatory problems are also commonly observed in these dogs.
- Those affected may also exhibit abnormal behavior―they do not respond to our calls. This is probably due to hearing impairments and other physical problems that makes them least interested in any kind of activity.
Kenny the White Tiger
Kenny, a white tiger that was born in captivity in Turpentine Creek, a wildlife refuge located in Southern region of the United States, breathed its last in 2008. The tiger was said to be suffering from Down syndrome. It was an inbred white tiger, meaning, it was born from mating related animals. In this case, Kenny's parents were siblings.
Inbreeding of white tigers was a common practice until in June 2011, it was officially banned by the American Zoological Association. This is because inbreeding limits the genetic range available to produce offspring. A wide genetic variation is necessary to produce healthy offspring. Purebred animals are born with limited genetic stock, which predisposes them to genetic problems. The best example would be Kenny the tiger, who showed inborn mental deficits. Kenny was mentally retarded and showed various cognitive disorders. As far as its facial features were concerned, the animal had a round face, typical in Down syndrome.
Although the symptoms were similar to that of Down syndrome, this mental deficiency occurs due to extra copy of chromosome 21 in humans, but tigers have only 19 chromosomes. Moreover, it is difficult to figure out whether abnormal division in any chromosome was responsible for causing this delay in mental retardation.
Can Cats Have Down Syndrome?
Unlike humans, cats have only 19 pairs of chromosomes. Since they don't have chromosome 21, they cannot get Down syndrome. However, cats may suffer from other chromosomal conditions such as Klinefelter syndrome that can also cause cognitive and developmental impairment. Cats with this condition appear overly large, have unusual facial features, and gain weight very rapidly.
In general, defect in chromosome no. 21 is the underlying cause of Down syndrome. Not all animals have the 21st pair of chromosomes, as found in cats. However, animals may have an extra copy of some other chromosome, which may cause genetic disorders that may mimic the symptoms of Down syndrome.
Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a veterinarian.