Genetic load and heterozygosity in the Pinaceae
Lethal genetic load might be caused by a few lethal genes or by large numbers of mildly deleterious polygenes. The extent of this lethal load can be quantified as the number of "lethal equivalents" in each individual. If there are large numbers of deleterious genes scattered throughout the genome then we might expect a correlation between the number of lethal equivalents and the level of heterozygosity at isozyme marker loci. Using data from 52 isozyme loci, we estimated this correlation on 68 individuals in four conifer species (Pinus ponderosa Laws., Pinus contorta Dougl., Picea glauca (Moench) Voss., and Pseudotsuga menziesii (Mirb.) Franco). No significant correlation was detected. We interpret this consistent result in four species as indicating that lethal equivalents do not represent large numbers of mildly deleterious polygenes in these forest trees.Key words: genetic load, lethal equivalent, Pinaceae, heterozygosity.
Mitchell-Olds, T; Guries, RP
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