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Thread: Dog questions

  1. #1 Dog questions 
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    "The origin of the domestic dog (Canis lupus familiaris) began with the domestication of the gray wolf (Canis lupus) several tens of thousands of years ago."
    http://en.wikipedia.org/wiki/Origin_of_the_domestic_dog

    If the domestication had not occurred, all the (artificial-selection) dog breeds that we see today would not exist?

    The DNA must be different in each breed, to produce each unique skull, body size, etc...

    How is the DNA actually changed during the process of breeding?

    Could a Chihuahua be bred back to a gray wolf?


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  3. #2  
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    Do a google search on Mendel, never mind, I did it for you.

    http://en.wikipedia.org/wiki/Gregor_mendel


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  4. #3  
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    Thanks,
    "Gregor Johann Mendel (1822 - 1884) was an Austrian Augustinian monk and scientist, who gained posthumous fame as the figurehead
    of the new science of genetics for his study of the inheritance of certain traits in pea plants."

    Note, the traits were "in" pea plants; the offspring had traits inherited from the parents.
    If there were green and yellow peas, the offspring were green or yellow, in a specific numerical pattern.
    His work explained the operation of dominant and recessive traits produced by "simple" genes.
    Could Mendel produce blue or red peas from those same parents?

    Would you not agree that dogs today have different DNA options than their ancestors?

    My question is: Considering one set of Wolf parents and how germ cells operate, how did the DNA options change?
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  5. #4  
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    I'm a little hazy on what your questions are, gs. Are you asking how selective breeding gives rise to distinct breeds and what genetic changes underlie the process? You seem to be wondering where the 'new' variations come from as well, is that correct?
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  6. #5  
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    Yes, how DNA is affected by selective breeding.

    Perhaps (many years ago) John, Mary, and their kids captured pups from wild Canis lupus parents.
    The pups grew up, establishing a closeness to John's family.
    Did that change the pups' DNA?

    As the pups matured and mated, would their pups have revised DNA?

    At what point, and how are different DNA options made available in the germ cells?
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  7. #6  
    Forum Radioactive Isotope skeptic's Avatar
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    When our ancestors first adopted wolf cubs to live among them, some would have grown up aggressive and some relatively tamer. It seems rather probable that the aggressive ones would have received a bop on the head. Over many generations, this elimination of aggression would result in breeding for tameness.

    Fortunately, we have a very good illustration of what breeding for tameness can do. The Russian scientist, Dr. Belyaev, carried out such an experiment on silver foxes. By breeding purely for tameness, he also found a number of characteristics appearing that are also found in dogs, but not wolves.
    http://www.suite101.com/content/dome...ver-fox-a68305
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    The consensus is that genes were modified.

    “Forty genes were found to differ between the domesticated and non-domesticated farm-raised foxes,
    although about 2,700 genes differed between the wild foxes and either set of farm-raised foxes.”
    http://en.wikipedia.org/wiki/Domesti...ox#cite_note-4

    Tegan Whalan provided interesting comments on the fox project:
    “Domestication/tamability is behaviour that is rooted in physiological changes and systems (e.g. hormones and neurochemicals). Changing these complex systems would have far-reaching effects on the development of the animals themselves. And as all mammals are controlled by similar bigger-regulatory systems, this is seen as a reasonable explanation for the changes.”
    http://leemakennels.com/blog/the-ori...0%93-part-iii/

    My question remains:

    How are the genes actually modified in the germ cell’s DNA so the behaviours can be inherited?
    Surely there must be more than bopping on the head...
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  9. #8  
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    gs

    The genetic variation is natural. Every individual is genetically different from every other. "Bopping on the head" simply selects out one set of individuals and removes their genes from the gene pool.
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  10. #9  
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    would have received a bop on the head :P
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  11. #10  
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    skeptic:

    “Bopping on the head”; I thought you meant that a human would discipline the young animal showing aggressive traits. But “remove from gene pool”; you mean the aggressive animals would be “terminated”; removed from the project?

    Why would a wild fox or wolf have any genes for tameness? How would these favor survival? Isn’t that group of 2,700 gene options a waste of resources?
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  12. #11  
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    Quote Originally Posted by gs99
    Why would a wild fox or wolf have any genes for tameness? How would these favor survival?
    For the same reason humans have genes for disadventageous conditions- they either emerge by chance or, in some cases, they had some other prior function or functions that are now no longer relevant under a new set of selective pressures. In either case, there's a lag time between a trait becoming disadvantageous and it disappearing from the gene pool depending on how significant the disadvantage is. That lag time is a window during which exaptation can occur.
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  13. #12  
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    If all wolves were equally and substantially aggressive, each would seek to be pack leader - alpha male - without respite. The result would be the death of all the wolves by internecine fights. Some wolves must be comparatively 'meek and mild', or 'tame'. Those are the ones that didn't get bopped on the head during the process of domestication.
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    “In either case, there's a lag time between a trait becoming disadvantageous and it disappearing from the gene pool depending on how significant the disadvantage is.”
    Wouldn’t tameness (as we see in various dog breeds) be a significant disadvantage for the wild wolf?

    Wolves evidently have had enough genetic variety to continue their successful existence with several dynamic social structures. (See quotation About Wolves below.)
    How could their DNA provide this (wild) variety plus other options (tameness) never selected?

    Another question I asked before was: “Could a Chihuahua be bred back to a gray wolf?”
    I get the impression that some dog breeds have been developed by selecting gene problems. If this is true, then I couldn’t breed “backwards”, because one or more genes have been damaged.
    Considering the fox project, how many generations away from the original wild fox could the selection be reversed back to the original genes? It would be interesting to see the actual gene results of each step.


    About Wolves
    Barry Holstun Lopez says: “There is typically, an “alpha”, or primary, male that dominates the other males and an alpha female that dominates the other females. This alpha pair is thought to be the breeding pair, but there are a good many cases in captivity and in the wild where a lower-ranking male has bred with the alpha female. Females may head packs and they always strongly influence pack activities.

    An alpha animal may be alpha only at certain times for a specific reason, and, it should be noted, is alpha at the deference of the other wolves in the pack. The wolf is a social animal; it depends for its survival on cooperation, not strife.

    The social structure of a wolf pack is dynamic – subject to change, especially during the breeding season – and may be completely reversed during periods of play.”
    (book “Of Wolves and Men” pages 31-33)
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  15. #14  
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    Quote Originally Posted by gs99
    “In either case, there's a lag time between a trait becoming disadvantageous and it disappearing from the gene pool depending on how significant the disadvantage is.”
    Wouldn’t tameness (as we see in various dog breeds) be a significant disadvantage for the wild wolf?
    Not if the tameness were directed towards a species with a very broad sense of empathy resulting in a tendency to give food to animals that are friendly towards it. Humans will empathise with trees given half a chance. Also, one feature of what we call 'tameness' is a greater tolerance of human proximity. A wolf that can stand to get close to humans is a wolf that can steal food from humans better than it's peers.
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  16. #15  
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    “The first true wolves began to appear at the end of the Blancan North American Stage,”
    http://en.wikipedia.org/wiki/Gray_wolf
    “about 1,808,000 years ago.”
    http://en.wikipedia.org/wiki/Blancan
    “A study by the Kunming Institute of Zoology found that the domestic dog is descended from wolves tamed less than 16,300 years ago south of the Yangtse river in China.”
    http://en.wikipedia.org/wiki/Wolf#Domestication

    If I read this right, wolves have genes that functioned without humans for 99% of their history.

    At what point did they determine that getting close to and stealing food from humans is a desirable trait?
    How rare must it be in a normal biosphere that wolves need to get food in this way? They survived almost two million years without it!

    If a pack of wolves found themselves in that desperate situation (no “natural” food), why wouldn’t the aggressive alpha units lead the way to steal food? Or possibly they would view humans as small deer?
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  17. #16  
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    Quote Originally Posted by gs99
    At what point did they determine that getting close to and stealing food from humans is a desirable trait?
    They didn't. That's not how evolution works at all. There's no planning or intent to any of it. Variation is random. If we consider the one trait of being able to approach humans, some wolves might be reluctant to approach humans, others eager, others still any number of levels between those. Whichever variety happened to survive or reproduce the most was the one that prevailed. There was never a decision made by wolves to vary in this manner or that.
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  18. #17  
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    Quote Originally Posted by gs99
    skeptic:

    “Bopping on the head”; I thought you meant that a human would discipline the young animal showing aggressive traits. But “remove from gene pool”; you mean the aggressive animals would be “terminated”; removed from the project?

    Why would a wild fox or wolf have any genes for tameness? How would these favor survival? Isn’t that group of 2,700 gene options a waste of resources?
    I use the possibly misleading term 'bop on the head' (sorry about that) because this happened during stone age times, and to kill an overly aggressive wolf would have been done with club or stone axe.

    I do not think they had genes for tameness per se. As I understand it, during the silver fox experiment, the main change discovered was a reduction in adrenalin production.
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  19. #18  
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    Thanks for the info. :-D
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  20. #19  
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    Quote Originally Posted by skeptic
    I do not think they had genes for tameness per se. As I understand it, during the silver fox experiment, the main change discovered was a reduction in adrenalin production.
    So you don't want to call them "genes for tameness".

    But the article said many genes were involved in the transformation. If these genes are seen to be the difference between wild and tame, why not call them "genes for tameness"? Some of these genes may be included in another group for another discussion, but here we're discussing the gradual change from wild to tame.

    "Forty genes were found to differ between the domesticated and non-domesticated farm-raised foxes,
    although about 2,700 genes differed between the wild foxes and either set of farm-raised foxes."
    http://en.wikipedia.org/wiki/Domesti...ox#cite_note-4

    How were they different? This could mean completely different genes or the same genes are modified in some way.

    My basic curiosity is: How did the genetic variation change?
    Which of the 2,700 genes came "to differ" first? And then what other gene was made "to differ"?
    Wouldn't it be helpful to repeat the experiment and have DNA documentation at each step?
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  21. #20  
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    I can only read the reports. According to those reports, the main physiological change seen was a major reduction in adrenalin. This was ascribed to be the main cause for a drop in aggressiveness (hence tameness) and the side effects including floppy ears, dappled colours etc.

    The drop in adrenalin would be the result of a genetic change, since it is a trait passed on through the generations. You could call that genetic change "genes for tameness" if you wish.
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  22. #21  
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    Quote Originally Posted by skeptic
    The drop in adrenalin would be the result of a genetic change, since it is a trait passed on through the generations.
    A 2004 Nova program also mentioned adrenalin as the “initial factor” in the fox project.
    From the partial transcript below, here are a few quotes:

    #1-NARRATOR: (about inherited genes) “if the parents don't have it, the pup can't get it.”
    #2-NARRATOR: “They checked the foxes' adrenaline levels—that's the hormone that controls the "fight or flight" response—and they found they were far lower than normal.”
    #3-NARRATOR: “As Belyaev bred his foxes for tameness, over the generations their bodies began producing different levels of a whole range of hormones.”

    I understand that alpha wolves do the mating. Therefore, it seems likely that most offspring would not be suffering from adrenalin levels “far lower than normal”.

    Questions:
    If the parents “didn’t have it” (adrenaline levels far lower than normal),
    how could the pups “get it” (adrenaline levels far lower than normal)?
    How could the pups (after x generations) begin producing levels of hormones different than their ancestors?
    For example, if the parents had specified values of 116 and 124, how could the new pups have genes that specified any other value?

    The explanation provided by Nova appears that If certain wolves stayed around the human camp to get handouts, the DNA in their germ cells changed.


    Transcript from Nova program “Dogs and More Dogs” PBS Airdate: February 3, 2004
    http://www.pbs.org/wgbh/nova/transcripts/3103_dogs.html

    #1-NARRATOR: Traits like coat color, or the way a dog carries its ears or tail, are determined by its genes. Genes are pieces of DNA, and they often come in subtly different versions. Every dog gets one copy of every gene from mom and one from dad. These genes can be mixed and matched in countless ways, but if the parents don't have it, the pup can't get it.
    And that's what makes curly tails and patchy coats in dogs so mysterious. Wolves don't have them. It took a remarkable experiment in a most unlikely place, to solve this mystery. The place was the middle of nowhere, Siberia. And the experimenter was an out-of-favor Russian geneticist named Dmitri Belyaev.
    Local fox farmers had asked Belyaev for help in breeding a less vicious animal. Belyaev began with the tamest foxes he could find. From their offspring, and for many generations thereafter, he chose only the tamest for breeding. He'd expected that each new generation would be a little less vicious, a little more tame. But by the tenth generation, he was seeing things he'd never expected.
    RAY COPPINGER: All of a sudden his fox ears started down, his fox tails started up, they started to bark, which is not characteristic of foxes. They started to have different coats, all these little features that you can't imagine being in the wild type. I mean it's not a matter of selecting for, because they're not there to be selected for—that variation isn't there.
    #2-NARRATOR: What does tameness have to do with ears, and barking and coat color? Belyaev and his colleagues immediately went looking for an explanation. They checked the foxes' adrenaline levels—that's the hormone that controls the "fight or flight" response—and they found they were far lower than normal.
    RAY COPPINGER: That would explain the tameness, they're just not afraid because they're not producing as much adrenaline. But where does the multi-colored coat come from? And somebody says right off the bat, "Hey, adrenaline's on a biochemical pathway that also goes to melanin, also has something to do with the animal's coat color." So there's a correlation between coat color now and the adrenal gland.
    #3-NARRATOR: Suddenly, it all started to make sense. As Belyaev bred his foxes for tameness, over the generations their bodies began producing different levels of a whole range of hormones. These hormones, in turn, set off a cascade of changes that somehow triggered a surprising degree of genetic variation.
    JAMES SERPELL: Just the simple act of selecting for tameness destabilized the genetic makeup of these animals in such a way that all sorts of stuff that you would never normally see in a wild population suddenly appeared.
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  23. #22  
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    Just a comment on the following statement :

    "The explanation provided by Nova appears that If certain wolves stayed around the human camp to get handouts, the DNA in their germ cells changed."

    I have a different explanation. We all know how many women, and children love to adopt puppies. You only have to look at how they react to puppies in a pet shop. It seems to me highly probable that wolf cubs would affect the same nurturing instinct, and lead to adoption of those wolf cubs.

    As those cubs grow up, some will prove to be aggressive, and dangerous. This is simply due to normal genetic variability. The men in the tribe that adopted the cubs will be a lot less 'loving' towards the wolves and will take the necessary action. That is, a whack on the head to kill the offending aggressive wolf.

    After many generations of wolves growing up, and the most aggressive being weeded out, adrenalin levels drop along with the development of tameness and the various other features associated with adrenalin drop.
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  24. #23  
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    There seems to be two guesses about how the dog started.
    1-Wolves hung around human camps to get food easier; natural selection followed.
    2-Humans obtained wolf pups and initiated artificial selection.

    Whichever way it happened, genes eventually came to differ, as shown in the fox experiment.

    I plan to start another thread to pursue my question in another way.
    See "Tale of Two Breeders".
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  25. #24  
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    Sorry, I have only read the OP, but a quick comment related to our distorted(simplistic) view of reality caused by the using of labels to identify what we talk about: Note that we often underestimate the genetic variance within a specific breed because they happen to "Look" in a similar way. You can not tell by looking at a human's outward appearance who is A negative blood from AB positive, and cant tell who has a genetic variation that prevents aids virus from attacking T-cells, we are all slightly mutants from one perspective.
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