Plant & Animal Genome VI Conference Plant & Animal Genome VI Conference
S10
Lehrstuhl fuer Tierzucht, Technische Universitaet Muenchen, Alte Akademie 12, 85350 Freising-Weihenstephan, GERMANY
Important traits of farm animals are mostly of a complex
nature. The term complex refers to any phenotype that does
not exhibit classic Mendelian recessive or dominant
inheritance attributable to a single locus (Lander
and Schork, Science 265: 2037-2048, 1994). The
complexity is based on the effects of multiple loci (and
their interactions) and / or high environmental noise. The
first steps of positional cloning of complex trait loci
consist of (1) the judicious choice of an animal material
ensuring maximum homogeneity and (2) the application of
phenotyping approaches that reveal robust 'endophenotypes'
(e.g., physiological parameters). Both careful selection of
the animal material (including the establishment of
suitable crosses) and 'endophenotyping' will often reduce
the complexity to an extent allowing straightforward
positional, especially positional (comparative) candidate
gene cloning. However, a major obstacle to positional
cloning of complex trait loci is the lack of mapping
precision that can be achieved with conventional linkage
analysis. Population-wide analysis of linkage
disequilibrium and the revival of the candidate gene
approach using DNA-chip-based genotyping open new
perspectives for systematic high-resolution mapping of
complex traits loci and their 'topical' cloning.