Simultaneous fine mapping of closely linked epistatic quantitative trait loci using combined linkage disequilibrium and linkage with a general pedigree

Causal mutations and their intra- and inter-locus interactions play a critical role in complex trait variation. It is often not easy to detect epistatic quantitative trait loci (QTL) due to complicated population structure requirements for detecting epistatic effects in linkage analysis studies and due to main effects often being hidden by interaction effects. Mapping their positions is even harder when they are closely linked. The data structure requirement may be overcome when information on linkage disequilibrium is used. We present an approach using a mixed linear model nested in an empirical Bayesian approach, which simultaneously takes into account additive, dominance and epistatic effects due to multiple QTL. The covariance structure used in the mixed linear model is based on combined linkage disequilibrium and linkage information. In a simulation study where there are complex epistatic interactions between QTL, it is possible to simultaneously map interacting QTL into a small region using the proposed approach. The estimated variance components are accurate and less biased with the proposed approach compared with traditional models.     

Stereoisomerization of the polycis compounds,pro-gamma-carotene and prolycopene in chickens and hens

Relatively large amounts of the polycis compounds, pro-γ-carotene and prolycopene were administered to chicks or hens. About four-fifths of the pigment was destroyed, and the rest occurred mainly in the feces. Far-reaching bio-stereoisomerization took place that yielded all-trans and some neo-forms of the compound administered, besides polycis isomers, in part possessing more cis double bonds than the starting material. Some observations on the behavior of all-trans-lycopene in chicks are reported.