Reaction norms

Schlichting, C. D. and Pigliucci, M. (1998), Phenotypic Evolution A Reaction Norm Perspective, Sinauer, Sunderland, MA. 

David Hull I think that reaction norms are absolutely essential to our understanding of genetics, evolution and what have you. I have an historical question to ask - Why has so little been written about reaction norms I realise that a book was published recently devoted entirely to reaction norms (Shlichting and Piglicci, 1998). With great enthusiasm, I bought the book, read it, and discovered I already knew everything in that book. Why is such an important notion left so unanalysed. 

Sohotra Sarkar. Which of those, penetrance, or the reaction norm ... 

David Hull. Reaction norms. Penetrance too, but primarily reaction norms. 

The history of the norm or reaction has been reconstructed by Sarkar (1999) - historical details in the rest of this paragraph are from this source. 

Sarkar, S. (1999), From (tie Reaklionsnorm to the adaptive norm the norm of reaction, 1909- I960 , Biology and Philosophy, 14, 235-252. 

Ken Schaffner Just a very brief comment before we go on. About three years ago, I was doing some work on C. elegans, and I asked Corey Bargman about norms of reaction. She s a distinguished UCSF experimentalist. She said she had never heard about it. At least in that term. After I described what it was, she said oh wait, we use that . But she d never heard of the terminology, and I suspect that it s just not widespread in the molecular community. 

Sohotra Sarkar By the way, one of the reasons why the paragraphs describing the importance of the norm of the reaction disappeared from the book is because one of the referees who read the book, reacted to those two paragraphs by claiming that the norm of reaction was the most useless thing ever introduced in genetics. 

Alex Rosenberg. This partly reflects the ideological split between Lewon-tin and some others with respect to the acceptance and the interpretation of molecular biology. The norm of reaction, as a concept, is closely associated with Lewontin, and as you point out both in your book and today, has an interesting Soviet pedigree. 

Sohotra Sarkar. Yes, and in fact the only reason the molecular work is being done right now - partly I agree with Alex - is those of us who do some of that work do not talk about the norm of the reaction at all, we replace it by talking about plasticity, but it s a cluster of concepts very connected to each other. 

The first addend is positive, and measures the direct effect of the rise of the co-payment rate. It expresses the effect of the normative change in the distribution of the financial burden between the two parties, before the user s reaction of restraint in the use of the pharmaceutical is taken into consideration. The other two addends are negative, and quantify the decrease in expenditure caused by the drop in consumption as a reaction to the rise in the price paid. The balance can have either sign, depending on the elasticity of demand and the size of the increase in the co-payment. In the example shown in Figure 7.3, despite a considerable decrease in the quantity consumed, the patient will end up paying more for the drag than before. 

Estimates based on European data are more scarce, and present other problems. In universal public insurance systems, in which financing is not based on premiums, there is no interpersonal (intra-group) variability in the drag copayment rates, or if there is it is very small. Therefore, temporal data are used to quantify the reactions of demand to normative changes in co-payment rates. The problem here is that such changes have occurred on very few occasions, and concurrently with other sources of variation in demand. 

The source of some of the difficulties encountered in trying to explain the effects of structural changes on ionization rates may be due to the different parts played by the solvent, as for example, the sulfur dioxide of the trityl chloride equilibrium experiments and the aqueous acetone of the benzhydryl chloride rate data. The solvent is bound to modify the effect of a substituent, and although the solvent is usually ignored in discussing substituent effects this is because of a scarcity of usable data and not because the importance of the solvent is not realized "... solvation energy and entropy are the most characteristic determinants of reactions in solution, and... for this class of reactions no norm exists which does not take primary account of solvation. 220 Precisely how best to take account of solvation is an unanswered problem that is the subject of much current research. 

In the next section, the flame speed development of Zeldovich, Frank-Kamenetskii, and Semenov will be discussed. They essentially evaluate this term to eliminate the unknown ignition temperature 7] by following what is now the standard procedure of narrow reaction zone asymptotics, which assumes that the reaction rate decreases very rapidly with a decrease in temperature. Thus, in the course of the integration of the rate term lv in the reaction zone, they extend the limits over the entire flame temperature range T0 to T. This approach is, of course, especially valid for large activation energy chemical processes, which are usually the norm in flame studies. Anticipating this development, one sees that the temperature term essentially becomes... 

The electrode potential of an electrode reaction at equilibrium can be measured as the electromotive force of an electrochemical cell composed of both the reaction electrode and the normed hydrogen electrode. The potential of the reaction electrode thus measured is taken as the equilibrium potential of the electrode reaction relative to the normal hydrogen electrode. 

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