Estimating lethal allele frequencies in complex pedigrees via gene dropping approach using the example of Brown Swiss cattle

Abstract. A new approach to estimating the allele frequencies of lethal autosomal-recessive genetic disorders was developed based on the gene dropping method. The method was tested in the complex pedigrees of 1 830 125 animals of the Austrian Brown Swiss population, where carriers for 4 genetic disorders were recorded. Trends of allele frequencies of Spinal Dysmyelination and Spinal Muscular Atrophy increased while Weaver decreased, but allele frequencies of Arachnomelia fluctuated between 2 and 3 %. The results were compared to the results from other methods. The results obtained from probability of gene origin were higher than the results from gene dropping in general, while the results from gene counting were lowest due to the fact that just a part of the pedigree information could be considered by the used program. The gene dropping and gene counting methods used here take lethal selection into account, while the program based on probability of gene origin does not. Therefore, gene dropping and gene counting seem to be more appropriate for estimating the lethal allele frequency of lethal autosomal-recessive genetic disorders. Applying the gene dropping approach, one can obtain the distribution of allele frequencies and confidence intervals for the allele frequency, which might be valuable for observing trends in active breeding populations.