noun, plural: purebreds
A purebred refers to offspring resulting from a true breeding. True breeding is a way to produce offspring that would carry the same phenotype as the parents. Thus, a purebred would result when the parents are homozygous for certain traits. A purebred of domesticated animal or a pet animal can be achieved through the process of selective breeding. For example, two dogs of the same breed would have an offspring with rather predictable traits. Nevertheless, selective breeding between same breed would be disadvantageous in terms of gene pool. True breeding tend to limit the gene pool. A large gene pool means greater genetic diversity. And higher genetic diversity could mean increased chances of biological fitness, and therefore of survival. In contrast, a gene pool that is restricted could lead to low genetic diversity. This reduces the chances of inheriting favourable traits that increase biological fitness. Purebreds are susceptible to acquiring genetic diseases or congenital health problems because of limited gene pool.