Selection Differential ☆

Author(s):  
W.G. Hill
2021 ◽  
Vol 3 (2) ◽  
pp. 27-32
Author(s):  
I. M. Fefelova ◽  
◽  
V. I. Lytvynenko ◽  
A. O. Fefelov ◽  
◽  
...  

This work discusses the problem of forecasting the tertiary structure of a protein, based on its primary sequence. The problem is that science, with all its computing power and a set of experimental data, has not learned to build models that describe the process of protein molecule coagulation and predict the tertiary structure of a protein, based on its primary structure. However, it is wrong to assume that nothing is happening in this field of science. The regularities of folding (convolution) of the protein are known, methods for its modelling have been developed. Analysis of the current state of research in the field of these problems indicates the presence of shortcomings associated with the accuracy of forecasting and the time necessary to obtain the optimal solution. Consequently, the development of new computational methods, deprived of these shortcomings, seems relevant. In this work, the authors focused on the lattice model, which is a special case of the known hydrophobic-polar dill. protein conformation according to the chosen model, hybrid algorithms of cloning selection, differential are proposed. Since the processes of protein coagulation have not been fully understood, the researchers proposed several simplified models based on the physical properties of molecules and which leads to problems of combinatorial optimization. A hydrophobic-polar simplified model on the planar triangular lattice is chosen as a protein model. From the point of view of the optimization problem, the problem of protein folding comes down to finding a conformation with minimal energy. In lattice models, the conformation is represented as a non-self-cutting pathway. A hybrid artificial immune system in the form of a combination of clonal selection and differential evolution algorithms is proposed to solve this problem. The paper proposes a hybrid method and algorithm to solve the protein folding problem using the HP model on a planar triangular lattice. In this paper, a hybrid method and algorithm for solving the protein folding problem using the HP model on a planar triangular lattice are proposed. The developed hybrid algorithm uses special methods for encoding and decoding individuals, as well as the affinity function, which allows reducing the number of incorrect conformations (self-cutting solutions). Experimental studies on test hp-sequences were conducted to verify the effectiveness of the algorithm. The results of these experiments showed some advantages of the developed algorithm over other known methods. Experiments have been taught to verify the effectiveness of the proposed approach. The results labelled "Best" show the minimum energy values achieved over 30 runs, while the results labelled "Medium" show the robustness of the algorithm to achieve minima. Regarding robustness, the hybrid algorithm also offers an advantage, showing higher results. A comparative analysis of the performance results of the proposed algorithm on test sequences with similar results of other published methods allows us to conclude the high efficiency of the developed method. In particular, the result is more stable, and, in some cases, conformations with lower energy are obtained. Keywords: protein folding; hydrophobic-polar model; clonal selection; differential evolution; artificial immune systems; hydrophobic-polar model.


1954 ◽  
Vol 1954 ◽  
pp. 75-82 ◽  
Author(s):  
A. T. G. McArthur

The main object of the artificial insemination service is herd improvement. This is facilitated by the larger selection differential obtained when only a small number of bulls are used. Robertson and Rendel (1954) have shown that artificially bred daughters by bulls used at centres outwith the Milk Marketing Board system did not outyield naturally bred daughters milking in the same herds and these results have been substantiated by data from the Board’s centres. This failure to select bulls better than those used in the average herd has probably been due to the multiple aims of selection necessary to satisfy all those interested in the artificial breeding movement and to the methods which have been used to evaluate bulls. A method has been designed aimed at improving this evaluation.


1971 ◽  
Vol 51 (3) ◽  
pp. 187-192 ◽  
Author(s):  
J. PESEK ◽  
R. J. BAKER

A simple method of calculating standard errors of heritability estimates is presented. The method is then used to conclude that observed response to selection for yield in five different populations of common wheat, Triticum aestivum L., agreed with the response predicted by multiplying estimates of heritability by the selection differential. It is suggested that a comparison of observed and predicted responses is not the best way to test the theory used in predicting response to selection.


2016 ◽  
Vol 44 (1) ◽  
Author(s):  
J.S. Minimol, B. Suma, Mahiya Ummer P.A. Jayasree

<p>Vascular streak die back (VSD) disease caused by <em>Oncobasidium theobromae </em>(now renamed as <em>Ceratobasidium theobromae</em>), is one of the major threats in cocoa growing countries, mainly becauseit cannot be controlled by any chemical application. In India, this disease outbreak took place during 1990 and it became an unmanageable problem of cocoa trees. Knowing the importance of resistant hybrids for controlling this disease, Kerala Agricultural University took up resistant breeding programme. It was a massive breeding programme which resulted in production of 5921 hybrid seedlings. After nursery screening of these hybrids by subjecting to heavy inoculation load for more than two years from March 1996 to June 1998, only 566 seedlings survived and they were field planted during June 1998. When relative efficiency of mother plants to transfer resistance to their progenies was estimated, it was seen that G VI 126 (Scavina 6) showed maximum recovery of 32.6 per cent after fifteen years of screening. Comparison of efficacy of male parents indicated that G VI 55 showed maximum recovery of resistant parents (168 nos.). During the entire period of investigation, 267 hybrids were found free from the disease. Out of this, only 51 recorded satisfactory yield levels. All these hybrids showed high value for selection differential (S) indicating maximum genetic gain.These hybrids can be used as mother plants for establishing polyclonal garden, as VSD disease resistance is highly heritable and polygenically controlled. The resistant hybrids identified (both high and low yield) can be utilized for further studies employing conventional and molecular breeding methods.</p>


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