Genotyping California Condors for Pedigree Analysis and Genetic Map Construction

The conservation of the highly endangered California condor has been a principal focus of the Zoological Society of San Diego for years, and the Genetics Division of CRES has been a founding partner in this multi-disciplinary effort. The first contribution by Genetics began in 1981 with the request from the California Condor Recovery Team to develop a non-invasive method for determining the sex of every condor, and the genetic sexing continues on an annual basis for all new chicks.

The next major endeavor undertaken by Genetics was a study to determine the relatedness of all the founder birds and/or their first generation offspring using the technique of DNA fingerprinting. The fingerprinting data, which represent molecular profiles across multiple loci, were helpful in establishing some measure of relatedness in condors, but they could not be used to directly assess kinship. Dr. Charlie Geyer (then with the University of Washington) made the best statistical inferences about relationships he could and ended up dividing the condors into three clans. Dr. Jon Ballou and Recovery Team member Dr. Kathy Ralls (both at the National Zoo) then made their best estimates of kinship between all founders, assuming kinship between founders within the same clan was 0.25 and kinship between founders in different clans was zero.

These assumptions, which provided the basis by which the Recovery Team made management decisions, are still being used. However, advances in molecular genetics have provided a method that will allow a closer examination of relatedness in the condor population through the generation and analysis of molecular markers known as microsatellites. This process, known as genotyping, examines the molecular sizes of alleles produced at specific loci on the chromosomes. The alleles (two per locus and visualized by peaks or bands) of individual birds can be directly compared at each locus of interest, allowing for more precise calculations of kinship. The resulting data is being compiled and analysis made from comparisons between each pair of founders and then from comparisons of birds other than the founders. Microsatellites are also useful because the two alleles at each locus are inherited in Mendelian fashion (one from each parent), and genotyping has become the standard method for making parentage determination in a number of animal species.

The microsatellite results are being used to verify parentage in the wild-hatched condor chicks, providing CRES Fellow Dr. Allan Mee and the field biologists an important tool to confirm behavioral observations.

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