Definition

A human-controlled breeding programme in which specific plants or animals are chosen to breed (produce offspring) because they have particularly useful or valuable features. The aim is to produce offspring with specific characteristics.

Brief Explanation

Breeders of animals and plants in today’s world are looking to produce organisms that will possess desirable characteristics, such as high crop yields, resistance to disease, high growth rate and many other phenotypical characteristics that will benefit the organism and species in the long term. In the commercial pet trade, selective breeding is often employed to produce creatures with more aesthetic attributes such as attractive hair, unusual colour schemes or to manipulate the size of the animal. This process often takes place wherever there is a financial gain to be made from offering unique specimens in a niche market, and is most prevalent amongst dogs, cats and exotic pets such as Bearded Dragons.

Selective breeding or artificial selection is usually done by crossing two members of the same species which possess dominant alleles for particular genes, such as long life and quick metabolism in one organism crossed with another organism possessing genes for fast growth and high yield. Since both these organisms have dominant genes for these desirable characteristics, when they are crossed they will produce at least some offspring that will show ALL of these desirable characteristics. When such a cross occurs, the offspring is termed a hybrid, produced from two genetically dissimilar parents which usually produces offspring with more desirable qualities. Breeders continuously track which characteristics are possessed by each organism so when the breeding season comes once again, they can selectively breed the organisms to produce more favourable qualities in the offspring.

The offspring will become heterozygous, meaning the allele for each characteristic will possess one dominant and one recessive gene. Most professional breeders have a true breeding cross (ie AAbb with AAbb) so that they will produce a gene bank of these qualities that can be crossed with aaBB to produce heterozygous offspring. This way the dominant features are retained in the first breeding group and can be passed on to offspring in the second instance.

This process of selecting parents is called artificial selection, and poses no threat to nature from man manipulating the course of nature. It has allowed our species to manipulate and increase the efficiency of the animals and plants we breed, such as increasing milk yield from cows by continuously breeding selected cows with one another to produce a hybrid.