Down syndrome is a genetic condition that affects the way the body develops and functions. It is a part of the human genome and is found in every cell. Chromosomes contain a person’s genes, which carry the codes for all our inherited traits. Each person has 23 pairs of chromosomes.
Trisomy 21
A fetus with Down syndrome has three full copies of the 21st chromosome instead of the normal two. This is caused by a mistake during cell division. Most people with Down syndrome also have an extra chromosome 13 (which isn’t associated with mental abilities). They can also have other symptoms such as clubbed digits, a bent pinkie toe, a wide 1-2 toe hole, and abbreviated height. Down syndrome can be found in chimpanzees as well, because they are human’s closest genetic relatives. Their 22nd chromosome is homologous to the human chromosome 21, so a trisomy in this chromosome can cause similar Down syndrome symptoms.
Chimpanzees normally have 24 pairs of chromosomes for a total of 48, so having a third copy of chromosome 22 is rare. Scientists recently confirmed the first documented case of this in a chimp named Kanako. The chimp was born in captivity at the Kumamoto Sanctuary in Japan. As a baby, she developed several characteristics that set her apart from other chimps. She had crossed eyes, which she retained into adulthood, and cataracts that caused her to go blind at age seven. She also had underdeveloped teeth and cardiac irregularities. During a routine physical exam in 2014, researchers found that she had an atrial septal defect, which is a hole in the wall that separates her heart’s top two chambers. This prompted them to analyze her chromosomes, which eventually confirmed that she has trisomy 22.
Kanako’s condition is helping scientists learn more about the effects of Down syndrome in chimps. She is housed separately from other chimps to avoid aggressive interactions but is allowed to interact with another female chimp on a regular basis. Her behavior and health are being carefully monitored and researchers hope to determine whether her condition has any impact on her ability to socialize.
Until recently, the only other known cases of Down syndrome in nonhuman animals were in dogs and pigs. However, a team of scientists in Korea has now successfully genetically engineered mice that have a trisomy in chromosome 16. This is allowing them to study the genetic causes of the disorder and how it affects the animal’s behavior.
Translocation
While we can’t see animals with Down syndrome (the disease is unique to human chromosomes) we can observe many other conditions that look like Down Syndrome. These are called translocations and they occur when parts of the chromosome move from their normal location into another part of the DNA. These parts are then copied every time the cell divides and pass on to any future offspring.
Chimpanzees are our closest genetic relative and some have been shown to have trisomy of the 22nd chromosome, similar to Down Syndrome in humans. This condition was first documented in 1969. However, it is very rare and scientists are not sure how frequently chimps develop this anomaly.
The most common type of translocation is a Robertsonian translocation, which occurs when a piece of chromosome 21 breaks off from the rest of the chromosome and moves to another part of the DNA. This results in three copies of chromosome 21, and Down Syndrome.
Some chromosomal abnormalities are more serious than others, and these have an impact on appearance and life expectancy. A chromosomal disorder is considered severe when there are multiple genetic anomalies in the individual. The more abnormalities an individual has, the greater their chance of having a child with Down Syndrome.
Despite being extremely close to us, monkeys cannot have Down Syndrome. They have 23 pairs of chromosomes, and Down Syndrome only occurs in people who have three copies of chromosome 21. However, monkeys can have other conditions that resemble Down Syndrome, such as trisomy of the 22nd chromosome, which is found in chimps and was first recorded in 1992.
This chimp, named Kanako, was born with trisomy 22, which caused her to have blindness and stunted growth. Her mother rejected her, and she was raised by caretakers. She has a female friend with whom she interacts regularly.
Many white tigers are sold to the public as being “animals with Down syndrome.” Kenny, a white tiger rescued from an unethical breeder by Arkansas’ Turpentine Creek Wildlife Refuge in 2002, is one example of this mistake. His deformities, such as crossed eyes and orange skin, are due to generations of inbreeding and not a chromosomal mutation similar to Down Syndrome.
Mosaicism
Down syndrome is a chromosomal condition that occurs when an extra chromosome develops in the cell. This extra chromosome can cause various physical and mental developmental problems for the sufferer, including intellectual disability, low muscle tone, and protruding tongues. Although there have been some studies suggesting that animals can experience Down syndrome, until recently only two cases of monkeys with down syndrome have been documented.
In both cases, the monkeys with down syndrome were born with a mixture of cells that contained different chromosomes. This is called mosaicism, and it is an important aspect of chromosomal abnormalities. Mosaicism can occur in any species of animal, but it is especially common in humans. In fact, many individuals with genetic mutations such as Down syndrome have mosaicism. Mosaicism can also lead to other health issues, such as congenital heart disease, birth defects, and developmental delays.
Chimpanzees are a type of monkey that is closely related to humans, and they share 99% of the same DNA. Because of this, it is possible for them to have mutations similar to those found in humans. In one case, a chimp named Kanako was born with a third copy of chromosome 22, which is known as trisomy 22. This chimp had crossed eyes, cataracts, and underdeveloped teeth. She was later diagnosed with Down syndrome, which caused her to have intellectual disabilities and delayed growth.
Scientists are not sure how often trisomy 22 appears in chimps, but they suspect it is fairly common. It is even more likely in chimps that are born via in vitro fertilization, because the process increases the likelihood of chromosome abnormalities.
The other case of a monkey with down syndrome was discovered in a chimp named Kumamoto. This chimp was born with a number of abnormal characteristics that were similar to those of Down syndrome, including hypodontia, cleft palate, and shortened limbs. She was also diagnosed with Down syndrome after her mother rejected her and she was raised by her caretakers. Kumamoto was later treated for a variety of health conditions, including vision problems and heart disease.
Genetics
As with humans, monkeys can have a duplication of their 21st chromosome and this is what causes them to develop Down syndrome. The condition is also known as Trisomy 21 because the affected individual has an extra copy of this chromosome. This extra genetic material creates various symptoms and it is these that distinguish the disease from other genetic diseases.
Sadly, a chimp called Kanako was born with this rare genetic disorder in captivity. Her caretakers didn’t realize this until a routine exam showed her to have a heart defect that included a hole in the wall separating her two upper chambers. During this time researchers discovered that her crossed eyes, the fact that she created waterfalls when she bathed, and her impaired vision all mirror the characteristics of Down syndrome.
She is the first chimpanzee with trisomy 22 to be documented and it isn’t clear how common this condition is among the animal kingdom. Animals do not have the type of prenatal testing available to us so a fetus that has a trisomy would often die before it was even born. However, if a human has a trisomy it can be detected and the appropriate treatment can begin immediately.
The chimps who have a duplication of chromosome 21 may also have other genetic conditions as well which could contribute to the development of their symptoms. For instance, some chimps with this mutation have a chromosome break which means that one of their chromosomes is missing or damaged. This can cause a number of different problems including leukemia and a shortened lifespan.
In the same way, other chimps have a chromosome deletion which could contribute to the development of Down Syndrome. This condition can lead to a number of issues including an increase in heart valve disease and other heart problems.
While it is true that there are many animals with a chromosomal abnormality like trisomy 21, the animals that have been plastered all over the internet such as Kenny the tiger’s wide-set eyes or Otto the kitten’s unusual face may simply be suffering from other genetic conditions that produce features similar to those seen in people with Down Syndrome. Mice, on the other hand, only have 19 pairs of chromosomes so a duplication of this chromosome wouldn’t have the same effects as in humans.