breeding truean organism that is not genetically variable for a particular character. Thus, crossing two parents (or self-pollinating one parent) of this type would produce offspring that were all identical with the parents. Such types are also known as ‘pure-breeding’ and were, for example, used by MENDEL in his experiments with the garden pea. In more precise terms, parents breed true when they are homozygous (see HOMOZYGOTE for a pair of ALLELES of a particular gene.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005