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A quick question about variability in genome


Nnicolette

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I was just wondering why humans and dogs have such a huge variability in dna expressions. Does anybody know why they can look so many different ways while other animals of the same species seem to all look the same? Is it because we are a combination of different species? If you find the time to enlighten me thank you.

Edited by Nnicolette
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1 hour ago, Nnicolette said:

I was just wondering why humans and dogs have such a huge variability in dna expressions. Does anybody know why they can look so many different ways while other animals of the same species seem to all look the same? Is it because we are a combination of different species? If you find the time to enlighten me thank you.

 

Interbreeding...
 

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The Incredible Explosion of Dog Breeds

From a teacup-size Chihuahua to a Great Dane, there is an incredible amount of variety among dog breeds. But all breeds belong to a single species, so scientists have studied the breeds to better understand the workings of evolution, and how such great variation could have arisen within one group.

 They found that all dogs belong to one lineage, which indicates that domestication occurred just one time. (If wolves were domesticated several times in various regions, the team would expect to find more than one lineage among modern dogs.)

Despite the fact that dogs were first domesticated about 14,000 to 17,000 years ago, most dog breeds were developed within the last few centuries. When ancient humans bred dogs for features such as a louder bark (for added protection of their owner's property) or a docile temperament (so it would be less likely to lash out at its owner), they were actually already tinkering with the selection of dog genes.  

http://www.livescience.com/8420-incredible-explosion-dog-breeds.html


 

 

How did we get so many dog breeds?

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Ancient dog breeds

Ancient breed of dogs was a term once used for a group of dog breeds by the American Kennel Club,[4] but no longer.[7] These breeds were referred to as "ancient breeds", as opposed to modern breeds, because historically it was believed that they had origins dating back over 500 years. In 2004, a study looked at the microsatellites of 414 purebred dogs representing 85 breeds. The study found that dog breeds were so genetically distinct that 99% of individual dogs could be correctly assigned to their breed based on their genotype, indicating that breeding barriers (pure-bred breeding) has led to distinct genetic units. The study identified 9 breeds that could be represented on the branches of a phylogenetic tree which grouped together with strong statistical support and could be separated from the other breeds with a modern European origin. These 9 breeds had been referred to as "ancient breeds", as opposed to the modern breeds. The study found that the Pharaoh Hound and Ibizan Hound were not as old as believed but had been recreated from combinations of other breeds, and that the Norwegian Elkhound grouped with the other European dogs despite reports of direct Scandinavian origins dating back 5,000 years.

https://en.m.wikipedia.org/wiki/Dog_breed#Ancient_dog_breeds

 

 

 

 

 

 

 

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2 hours ago, Nnicolette said:

I was just wondering why humans and dogs have such a huge variability in dna expressions. Does anybody know why they can look so many different ways while other animals of the same species seem to all look the same? Is it because we are a combination of different species? If you find the time to enlighten me thank you.

I'm certainly no expert, but I would say this. 

 The comparison between how well we see differences in our own species, and how well we see them in others may be very subjective. When we look at our own species we are constantly and unconsciously making decisions. Would I breed with them, are they a threat, are they like me, do I relate to them, how well will I be able to interact with them, and so on. It's likely that our perceptions in this regard are very heightened.  

Obviously there are differences, but then again look at wild wolf pack, and you'll see and equal amount of variation. Plus, as we're pretty much bald, instead of just seeing broad morphology and coat colour, we can focus on lots of little details we'd miss in other less familiar, fuzzy, species. 

As to whether it's because we carry traces of other 'species' or not isn't likely to be much of a factor. Firstly, because physically, the more obvious adaptations and variations seem in modern humans aren't related to this, but to traits our own branch has developed in its radiation into new environments.

Secondly, most species we see are at least similarly mixed up through hybridisation, both now and throughout their evolutionary history. As are we. 

Which leads to the third point, that the whole concept of species is a bit arbitrary anyway. There really isn't any agreed wholly subjective way to decide where to draw the line. And, the decision where to draw that line differs considerably. I recently heard there were around six various sets of criteria in use now. 

Dogs are a good example of this. Wolves and coyotes both carry each others genes as a result of longstanding and current hybridisation. As well as a portion of domestic dog DNA. They look pretty similar to each other, there's often niche overlap, and can interbreed. Yet, they're considered different species. 

To get past the sort of artificial trait selection that we've imposed on their wolf ancestors, which gives rise to the different breeds of domestic dogs. It's best to look at the wild dog species, who can all interbreed, to see how much natural variation there are in their appearance. And there's no more than there are for any similarly widely dispersed and abundant group. Cats for example. Which again, don't vary much except for size, and coat colour. But which show up some pretty bizarre morphs which have arisen from deliberate human selection. 

We're also much more familiar with dogs and humans than we are with any other group (possible exception being cats, but as above same thing). So we may not actually be familiar with how much variation there is between members of other groups. We just won't notice it.

Bottom line, the differences are essentially those we create, as in dogs. And over perceive, in relation to the way see less familiar animals. 

 

Edited by oldrover
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Any domestic species will have wild variation, be it dog, cat, cow, horse, hen, etc, simply because human are controlling the breeding to fit their own need (fast and slender dogs for hunters, beefy dog to guard, herding dog for the sheep, cute dog for rich ladies, fast and strong dog for dog sledge, etc.). Cats' variations are less wild because they aren't big enough or docile enough to be used for other thing than control vermin and please the ladies.

Also, a lot of dog breeds are rather modern, there was a Victorian craze over making brand new breeds for tiny local variation.

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