Read about how much DNA relatives share including siblings, twins & cousins, as well as what percentage of DNA humans share with dogs.
The next time you refer to someone as monkeying around you may not be that far from the truth. Chimpanzees are our closest relative as a species and we share at least 98% of our genome with them. Our feline friends share 90% of homologous genes with us, with dogs it is 82%, 80% with cows, 69% with rats and 67% with mice [1].
Human and chimpanzee DNA is so similar because the two species are so closely related. They both descended from a single ancestor species 6 or 7,000,000 years ago. As they evolved, their DNA changed as it was passed from generation to generation. It is these DNA changes that account for the differences between human and chimp appearance and behaviour.
By virtue of being the same species, all humans share 99% of their genome, which means that all humans are 99% genetically similar.
Our bodies are made up of 3 billion genetic building blocks, or base pairs. Of those 3 billion base pairs, only a tiny amount are unique to us. The remaining 1% of genes that are different explain the variations in characteristics, such as colour of hair, eyes and skin, and also risk for certain diseases.
When undertaking a paternity test, DNA samples from family members are analyzed. AlphaBiolabs examines short tandem repeat (STR) markers that are specific locations on chromosomes made up of sequences of repeated DNA. These STR markers are highly variable in length between individuals. Each individual has two copies of each STR marker, known as alleles: one is inherited from the father and the other from the mother. By looking at these specific DNA markers in each sample, it is possible to identify which half of the child’s DNA is inherited from the mother and which half is from the father.
How Do We Know What Percentage of DNA Two Species Share?
The most accurate way to identify exactly what percentage of DNA is shared by two species is to compare their complete DNA sequences (or genomes) with each other. However, determining the entire DNA sequence of an animal is a difficult task that takes significant time and effort. It requires a great deal of equipment, resources, and funding to do so.
The recipes in this DNA cookbook are written in a simple language with only the four letters A, T, G, and C as its alphabet. Doesn’t sound like enough letters but they are plenty because there are billions of them repeated and jumbled in so many different combinations. Which means that the DNA inside of you or a dog is really, really long.
Now the difference between people and dogs isn’t the number of recipes. Humans and dogs have about the same number of genes, about 20,000 or so. A human’s genes are split across 23 chromosomes while dogs have around the same number spread across 39 chromosomes. In a sense, humans and dogs have cookbooks filled with the same number of recipes.
Theres a lot of different ways to compare how similar two species are, so youll see different numbers for how much DNA dogs and humans share. But the group that first sequenced the dog genome found that they could match up about 73% of dog DNA to human DNA. And they found that almost all of a dogs genes are also found in humans.
This makes sense, because humans and dogs share so many similar body parts that carry out the same basic biological functions. They even share many kinds of genetic diseases – cancer, blindness, and congenital heart disease, for example. That’s why scientists have been turning to dogs as a model for studying human diseases.
Most of these differences are the result of having different letters in the recipes themselves or in the instructions in how to use them. In other words, some differences are in the genes themselves and some are in the DNA outside of the genes that tell a cell how often to read a gene.
How Much DNA Do We Share With Dogs?
The origin of modern dogs lies tens of thousands of years ago, but how does a wolf become a pomeranian?
Now renowned as a steady family pet, the labradoodle was invented in the 90s to be a low-allergen seeing-eye dog. The breed’s recent origin and portmanteau name makes it rather obvious that labradors and poodles were blended in the creation of the labradoodle. But what about the other 400 or so dog breeds – how does a wolf become a pomeranian?
The origin of modern dogs lies tens of thousands of years ago (somewhere between 20,000 and 40,000) when humans domesticated an ancient relative of today’s wolves. People have been carrying out deliberate, selective cross-breeding since then, initially creating dogs to specialise in herding, hunting and guarding.
Then came the Victorian breed explosion. In the mid-19th century there was a period of intense innovation and codification in dog breeding, giving rise not only to a diversity of breeds, but the very concept of “breed” itself. During this boom, disparate dog lineages were deliberately crossed to enhance favourable traits or dilute undesirable ones. Crossing was also done with the express purpose of creating novel breeds, selecting for aesthetic characteristics.
This created a messy, intertwined relationship between different dog types, with the details of a breed’s origin sometimes recorded only in oral history.
It wasn’t until a landmark genetic study was published in 2017 that we gained a clearer picture of how all these breeds relate to each other.
Researchers from the National Human Genome Research Institute in the US analysed DNA from 161 breeds to create a dog-breed family tree. The tree groups breeds into categories according to their shared history. These groups, known as clades, reflect the fact that for much of their domestication history dogs were known only by the kind of service they offered humankind. The hunting dogs are a family including retrievers and setters, the herding dogs contain the shepherds and sheepdogs.
Dr Elaine Ostrander is the head of cancer genetics and comparative genomics at the institute and was the supervising researcher on the 2017 study, as part of the NHGRI’s dog genome project.
“What we wanted to know was, how do dog breeds relate to one another?” she said.
“We know most breeds have only been around since Victorian times. There were fanciers in Europe who wanted to create breeds that had a particular appearance or have a particular skill or personality.”
“One of the things that is important is geographical location – where the breeds were developed,” she said.
“Function was certainly important as well, and there certainly is a relationship among dogs with the same appearance, like the miniature and standard schnauzers.
While the genomes of all dogs are 100% dog DNA, a small amount of the genome varies among breeds. These parts are responsible for the impressive spectrum of variation in size, shape and behaviour in domestic dogs. The researchers sequenced dog genomes at thousands of these variable sites. When blocks of them are identical across two different breeds, this indicates historic interbreeding between them.
These fresh results confirmed documented histories for some breeds. Heidi Parker, the lead researcher on the study and also a geneticist at NHGRI, said the results also showed evidence of crosses that were not documented or were otherwise unexpected.
“We found out that the German shepherd was pretty much Italian,” she said. “I don’t know if we know what the German shepherd story actually is yet, other than it’s one of the breeds that shows up with the most outcrosses to various things.”
Here we’ve used the data from the genetic study to visualise the relatedness between a single breed and all the other breeds they examined (where the relatedness was over a certain threshold – see the notes below for more details): How closely related is the German Shepherd to other breeds? Showing a relatedness index between two breeds based on identical-by-descent haplotype sharing which measures identical sections of DNA inherited from a common ancestor View by breed View by group Relatedness index
In this example, you can see the German shepherd shares larger amounts of DNA with the cane paratore, berger picard and chinook. It’s important to note that these graphics do not indicate the direction of the cross – only that two breeds are more or less closely related.
“We don’t know the directionality, it just tells us there has been mixing and matching between breeds,” Ostrander said.
In some cases, much older breed histories were able to be confirmed. A beast of legend, the original Irish wolfhound, had not been seen for almost 100 years and was presumed extinct. In the 1860s George Augustus Graham set about recreating it from existing dog lineages, starting with Scottish deerhound stock and sprinkling in some great dane for added size. How closely related is the Irish Wolfhound to other breeds? Showing a relatedness index between two breeds based on identical-by-descent haplotype sharing which measures identical sections of DNA inherited from a common ancestor View by breed View by group Relatedness index
The results for the pug – originally from China – were surprising. Breeders have sprinkled a dash of pug genes into a wide variety of breeds throughout the world, presumably to make them smaller. How closely related is the Pug to other breeds? Showing a relatedness index between two breeds based on identical-by-descent haplotype sharing which measures identical sections of DNA inherited from a common ancestor View by breed View by group Relatedness index
Here you can select any breed included in the study to view the relatedness to other breeds, or try one of the groups to see a bigger picture of connections between breeds. How closely related to other breeds? Showing a relatedness index between two breeds based on identical-by-descent haplotype sharing which measures identical sections of DNA inherited from a common ancestor. COO or USA denotes if a dog was sampled from the country of breed origin (COO) or the United States View by breed View by group Relatedness index
One thing that’s missing from this analysis are so-called “designer breeds”, such as the goldendoodle or groodle, cavoodle and various other -oodles.
The reason for this is, according to Parker, that most of these dogs are not an ongoing breed.
“Most of those breeds, almost all of them, are created simply as one-offs. But they don’t continue,” she said. “The only group that’s really doing that is the labradoodles – the Australian labradoodle club.”
The NHGRI dog genome team has researched the labradoodle specifically, showing it is genetically more poodle than labrador.
Some dogs in the study, such as the dachshund or grey wolf had no links to other breeds. Parker said there are a few possible explanations for this.
“The sharing that we identified in the paper was about 200 years old or less. A couple of the breeds, like the dachshund and Dalmatian, show no bands of sharing at that age point,” she said.
“This could mean that these breeds were set in their current form before that time and no one has seen fit to play with that form. It is also possible that we just don’t have the correct breeds in the dataset to see other additions.
“That is one of the reasons we are still adding more breeds and especially regional breeds to our tree, to fill in the missing pieces.”
As for the future of the dog genome project, Ostrander says they are doing the same analysis between different breeds, using full genomes for comparison.
“One of the questions we’re dying to know the answer to is: what are the differences? What do you see that you didn’t see before with this much higher level of resolution?”
Groups used in the figures are the 23 clades given by Ostrander et al’s analysis, with clade-less breeds grouped into “other”.
Colours are mostly to indicate whether two dogs are in different clades, rather than to identify the specific clades as it’s very difficult to make a categorical colour key work with 23 colours.
The relatedness index simply uses a scale from 1 to 100 based on the smallest base-pair size match to the largest basepair size match. Only matches over 250,000 base pairs are included as in the original article.
This article was amended on 26 October 2020 to clarify that a boom in dog breeding happened in the 19th century, not the 18th century.