Visualization of Inheritance Patterns from Graphic Representation of Additive and Dominance Relationships Between Animals

¹ Department of Animal Sciences, University of Illinois, Urbana 61801

Evaluation of pedigrees of normal and affected individuals help to suggest possible patterns of inheritance. Because large numbers of individuals are involved in studies of genetic disease, classic two-dimensional family tree charts are difficult to draw. Instead, DFA plots of graduated circles, weighted by dominance relationships, inbreeding, and additive relationships between individuals can be plotted above, on, and below the diagonal. Base animals without phenotypic measurements contribute information for computation of approximate dominance relationships, inbreeding, and additive relationships, but are not explicitly in the graph. Plotting only a set of randomly selected animals for each combination of phenotypes improves the visualization effect, especially when pedigrees are large or when computer resources are limited. For deficiency of uridine monophosphate synthase and interdigital hyperplasia, DFA plots showed higher densities of additive and dominance relationships among affected animals. However, DFA plots did not show clear patterns of inheritance for heel erosion, laminitis, or sole ulcers because environmental effects were important for those traits. Grouped graduated circles also improved visualization. The function of DFA plots is comparable with statistical scatter plots that display data to help examine statistical approaches. The DFA plots serve as a first approach to evaluate genetic hypotheses before a more complex model is fit.

Key Words: graphs • additive relationship • inbreeding • inheritance

Submitted on July 28, 1994
Accepted on July 10, 1995