ABSTRACT
Population genetic theory has facilitated considerable progress in development of superior poultry breeding stocks through the use of selection and heterosis. The development of techniques for DNA fingerprint analyses provides tools that may be used to complement present breeding programs through direct identification of genotype. Based on the fact that the information obtained in these procedures is derived from many highly polymorphic loci inherited in a simple co-dominant Mendelian manner, five potential uses are described in this chapter:
Identification — A wide range of identifications is discussed: individual, family, genetic stocks, and breeding lines. The level of similarity between DNA fingerprint patterns of closely related populations as a relative estimate for genetic distance between them is also considered.
Evolution — Populations divergently selected for quantitative traits were shown to have specific DNA fingerprint patterns. These genomic differences are attributable to cumulative mutations and genetic drift through the process of many generations of selection, or to selection where alleles of the loci coding for the selected trait are linked to alleles of the DNA fingerprint loci. Two replicates of each of two Japanese quail lines divergently selected for 4-week body weight and one unselected line were used to demonstrate how these forces could generate line-specific DNA fingerprint patterns. The relative weight of these three evolutionary forces, namely, mutation, genetic drift, and selection, combined with a linkage disequilibrium state, were estimated to be 16%, 59%, and 25%, respectively.
Marker-assisted selection — An efficient approach to identify linkage between DNA fingerprint bands as genetic markers and quantitative trait loci (QTL) was based on a study of the paternal distribution of a quantitative trait combined with a comparison of DNA fingerprint patterns of DNA or blood mixes of individuals from the two extremes of the distribution of the trait in the population. This approach was demonstrated by an experiment in which a DNA fingerprint band was shown to be linked to abdominal fat deposition in broilers.
Genomic selection — Introgression of a given heritable trait from one line to a well-developed commercial line requires large numbers of backcross generations. To reduce the required number of backcross generations, an approach is presented for the faithful recovery of the recipient 244genome that involves selection based on an assessment of the level of DNA fingerprint similarity between progeny of the first and second backcross generations to the DNA fingerprint pattern of the recipient line (or minimum similarity to the donor line). This presentation is based on theoretical probabilities and on a brief description of experimental data.
Heterosis — Hybrid vigor is expected when lines involved in crossbreeding or the individual parents of a given cross are genetically distant. The larger the genetic distance, the larger the heterosis expected. An approach to predict hybrid vigor through selection of lines or individuals of minimum similarity between their DNA fingerprint patterns is discussed.
