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Subject: Re: [working-gundog] epigenetics and the origins of pointing

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jmurr

MH
Posts:158

07/11/2007 12:21 PM
----- Original Message ----- From: "Cj" \|... I don't know exactly how we could distinguish an epigenetic effect from a \| genetic effect with these dogs. If there are no differences that we can \| detect we have no hypothesis to test How do you suggest that we detect \| epigenetic effects? My argument is that we cannot now discriminate between \| genetic and epigenetic effects in pointing dogs. We do know that there is a \| pronounced tendency for dogs with a strong pointing instinct to produce \| offspring with that same instinct, e.g., that the pointing behavior has a \| genetic basis. ... I see two issues here. 1. Is there an epigenetic change brought about by young dog interaction with the environment which intensifies the point AND is inherited from that dog by its progeny? Testing this would obviously be tedious, but Stu may actually have been doing this with the wing-on-string segment of his breeding stock selection program for pointing Labradors. 2. Is there a gene or genes for pointing? If there is (are) one critical question which immediately arises is: What happens to the genome to intensify the point across generations? Is the sequence of bases on some gene(s) changed - do mutations occur? Is a new gene(s) inserted? I don't think these will prove to be the case. I suspect the UCD study will be unable to tell the difference between any genes associated with pointing from EPs and Munsterlanders (unless they find a difference in numbers of replicated copies in the genome? I am not clear on whether the technology planned is adequate to separate active genes from inactive (see below)) ................................. I suspect it will be found that there is no gene or collection of genes for pointing per se. It may be found that there are genes that code for certain chemicals used in many cellular construction processes such that: a. these genes exist in the genome as multiple copies, some "turned on," some "turned off." b. when these genes are expressed in certain areas of the brain during the time when neurons are being connected up to form behavior patterns (such as pointing); more "turned on" genes result in the production of more of some chemical critical for establishing certain connections associated with the "intensity" of the associated behavior, e.g. "point." c. during this period, interaction with environment can, through the epigenetic regulating chemicals also on site in the brain, cause some "turned off" genes to be "turned on" resulting in higher "intensity" in the individual affected. (There are alternative scenarios, e.g. the environmental interaction changes the concentration of epigenetic chemicals which in turn causes repeated expression of a single gene???) The natty question arises: Does the new mix of "turned on"/"turned off" genes get to the germ cells to be propagated to future generations? If it does, how? If this is not what happens, say the effect is entirely epigenetic, what is the nature of that information, and how does the information (now epigenetic) get to the germ cells for propagation?? I don't think these details are known now. They will be fascinating. Can I buy another 50 years? Jere

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