 Polygenic inheritance
Polygenic inheritance
Polygenic traits are controlled by an unknown number of genes. The gene expression is influenced by a variety of factors including gender, nutrition, breed, rate of growth, and amount of exercise. These traits are quantitative traits - that is, there is a wide range within the population. Such traits include height, weight, character, working abilities, and some genetic defects. Heritability varies within different breeds and within different populations of a particular breed.
Because it is virtually impossible to determine the exact genotype for such traits, it is difficult to control defects with a polygenic mode of inheritance. The best attempts at control are based on a grading scheme for identification of the defect and a breed policy of recording and publishing the results for as many dogs as possible. Canine hip dysplasia is a polygenic trait that remains a problem in most large breeds of dog, despite efforts to control this condition dating back to the 1960s. Breed organizations and veterinarians in various countries have developed control programmes that rely on radiographic evaluation and a central registry of dogs. Thoughtful selection by breeders, using this information, has greatly reduced the incidence of hip dysplasia in those breeds in particular countries. | 
11-08-2008, 01:35 PM
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