Explanation Of Gene Action As Related To Physiological

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-25- Hogsett: In my introduction off.Dr. Lush I failed to state that he has been the advisor for this group, I believe, ever since its inception and has done a fine Job in helping the committee plan the program. Now we will take as much time up to a half hour as you need to ask Dr. Lush any questions you may desire. Who will be first to ask a question? Parmenter: Msy I ask a question on this dwarfism in cattle, seeing that we are chicken breeders. What about the use of this profilometer on bulls, the accuracy of that? Lush: The experts on dwarfness in cattle are all meeting in Ames today. Several of them said they were sorry of the conflict, because they would have liked robe here. Certainly I would llke to have them here. Opinions differ on the accuracy of the profilometer. I do not know the very latest, but I think in general the opinion is that the accuracy is rather low. A good many people still think it has some accuracy. The profilometer is a device for running a wheel down the forehead of the animal, tracing on a piece of paper the profile as seen from a side view. It was based on the very logical thought that since the dwarfs have very bulging foreheads, maybe the heterozygotes would have a little bulginess. If so, you could find who could transmit dwarfness by examining their profiles. Some of the earlier work convinced Dr. Gregory that he was on the trail of something very important in this, but there are many statistical pitfalls of one kind or another in collecting and appraising this kind of evidence. Others went to work checking it. In the main the checks have not been very good. It still seems to me natural that the heterozygotes might show some bulginess. There was a lot of enthusiasm about the profilometer two or threm years ago but not many people are using it enthusiastically now. We are still trying it but we have pretty well lost faith in it. Hogsett: Any further questions?
-25- Wyatt: I would llke to ask Dr. Lush how you proceed in the case of mortality in chickens, for example. How do you go about finding one of these populations that you can use for a tester? How do you know how far this population is above the threshold and so forth? Lush: I expect there are some in the room that can answer that better than I. Maybe some of you think you haven't much difficulty in finding a population with low vitality! Seriously, the vitality must be above a certain minimum to keep them going, does it not? You could not have a tester population in which all died off before reproduction. They must have a certain amount of vitality to keep them going. Incidentally, you do not need a tester strain badly, as long as the mortality in the stock you are trying to improve is much above thirty per cent. Then mass selection and progeny testing can give about as much help as you can use. Even when you get the mortallty below thirty per cent, progeny testing and family or sib-testlng can help quite a bit until you get mortality on down toward _wenty or even fifteen. _hen the effectiveness of these begins to taper out. It does not_go completely to zero, but progeny tests and slb-tests diminish fast in their effectiveness when your mortality falls much below twenty per cent. Hence, I would not worry much about finding a tester stock until the mortality in my own stock was down under fifteen. If I ever got it under ten, then I would just about have to find a tester stock with high mortality. How I would find it, I am not sure. Maybe, if I did not have it in my own flock, my neighbors might sell me a stock which was low enough in vitality. Wyatt: Well, if you are going to measure this tester Just by the incidence of mortality in the tester, say that that is below the threshold, _hy can't you just measure the incidence of mortality in the flock you are
Page 1 and 2: "7-. J _ Gene Action as Related to
Page 3 and 4: dominance in their primary effects
Page 5 and 6: -ll- ! SUB-DIVISION OR CLASSIFICATI
Page 7 and 8: -13- A glance at this table reveals
Page 9 and 10: -15- genes have manyeffects, althou
Page 11 and 12: -I7- r effect of the gene, we also
Page 13 and 14: -19- be continued for several gener
Page 15 and 16: • -21- strains were very large. I
Page 17: "_3- ability" in general) is import
Page 21 and 22: -27- ! weakness in your stock you w
Page 23 and 24: -29- Hogsett: Dickerson: Dr. Dicker
Page 25 and 26: -31° We used to teach our classes
Page 27: -3_ that the pathogen, being a viru

Explanation Of Gene Action As Related To Physiological

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