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From phenotype to genotype: major genes in chickens
Published online by Cambridge University Press: 18 September 2007
Abstract
The relationships between phenotype and genotype were first described by Mendelian genetics in the case of genes with a major phenotypic effect. The remarkable improvement of biochemical and molecular tools has now made it possible to identify the molecular nature of major genes, and to understand better their mode of action. From a functional point of view, mutations of a given gene can be classified into three groups: loss of function, interference and dominant negative action, and gain of function. From a structural point of view, a large diversity of molecular polymorphisms can be found, the consequences of which depend rather on their position than on their nature. Genetic abnormalities or mutations with obvious morphological effects provide the most didactic examples to understand the genotype-phenotype relationships. The example of sex-linked dwarfism in chicken is described in detail and the present state of knowledge on the molecular identification of major genes in the chicken is reviewed. Finally, a general discussion, based upon examples taken from human genetics and mouse genetics, draws lessons from the study of major genes in order to approach the study of complex phenotypes or genotype x environment interactions.
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- Copyright © Cambridge University Press 2002
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