"If a specific gene has not been isolated, how do we know for sure that there is one, and that some horses are just carriers? "
It is called population genetics, I advise you get a book about it, in there it will expalin about genes and generational large scale inheritance patterns with respect to dominant and recessive genes.
How did researchers years ago know that in humans there are different blood types and their are specific inheritance patterns of those types???? and this was before DNA testing.
There is a mountain of information about inheritance of recessive genes and how generations can go on before it crops up.
I think you need to read some basic genetics books and specifically read about inheritance of recessive genes, because you just answered your own question. I am not making these terms up or these known genetic inheritance facts. These are genetic rules that have been scientifically proven. I applied genetic laws to my study and it fits.
Recessive genes exist in all living organisms even bacteria and viruses. They are not expressed unless certain conditions are met. This can be either by reproduction of the organism and the resulting offspring inherit it or like in certain bacteria can live in certain changing environmental conditions.
And no, dont get the idea that dwarfism is a gene that can willy nilly turn on or off, it is not that kind of gene. There are those kind of genes in us, yes, called regulatory genes of certain pathways, metabolism, digestion, etc.
If you are a carrier of a gene you have the gene in your DNA and can pass it on to your offspring.
"Do you believe that a dwarf can be produced if both parents are non-carriers, and normal horses? And by that I mean, are some dwarfs produced because environmental factors or trauma during pregnancy, like if the development and growth were disturbed by some factor other than a gene passed from a parent? If this is the case, will it really ever be possible to have a dwarf free breed?"
Two non-carriers (proven) will not produce a dwarf of that gene they are NOt carrying. If they are non-carriers of one type, yet are carriers of another type, they could have a dwarf of the other type they carry.
I have not read yet anything about dwarfism being caused by trauma, do you have a specific type of trauma you are thinking about????
Well I will say there are no dwarfs in the shetlands that I have seen documented, or the Hackney, or the POA, or the Arab, or the Welsh, or Caspian, Dartmoor pony. I dont know, how can they have breeds without dwarfism?? Maybe breed better horses??
Someone PLEASE bring me an example of your dwarf caused by an environmental factor, that you can definitively say is just that. I will never say that no unusual random event can't happen to then cause a dwarf. On the contrary, how do you think genes can get mutated, they mutate due to random events or influences. And no dont think that all these dwarfs are caused by random events causing the same gene to be mutated.
I would challenge anyone to find dwarf Miniature horses that they can prove was caused by a single common environmental factor all over the world that could be proven as the reason why we have all of these dwarf horses. Please go my son, make me proud.
What I am tryng to teach you is that look at your population of Miniatures, in all areas of the world. Now look at all the different environments they are in, now look at all the dwarf type 1 only that are born. Now, you tell me that one specific type with very similar characterisitics have a chance of being caused by something in the environment, ALL OVER THE WORLD. Which also would need to be in the exact same conditions. If just one of these dwarfisms was caused by even just 1 environmental factor, you would need a super computer to figure your odds to prove it is NOT being caused by a gene. This is becuase of the billions of variables because these dwarfs occur all over the world. The odds are tremendously in my favor of it being a recessive gene.
