However, where crossbreeding is a part of the system, naming the generations that comprise different proportions of genes from each original purebred can become quite complex. Figure 1 describes the accepted naming system for different crosses. Note that 'P' always means purebred, 'B' always means backcross to one of the original breeds and 'F' always means a hybrid or interbred hybrid. The use of standard naming systems ensures that everyone understands what is meant by each term. Animal breeding terms Alleles Alternative genes at a particular position on the chromosomes.
Alleles produce different effects on the same trait - for example, horns vs polls.
Matings between animals with similar characteristics. See disassortative mating. Breed A defined population of animals within a species that differs from other populations in respect of genetically determined traits. The additive effect of all genes that affect a trait. The value of an animal as a parent in terms of a trait, expressed as a genetic deviation from the average of a population.