But breeding is not about improving an individual animal per se — once it has been born you can’t refine it further by tinkering with its genome. Breeding is really about improving populations of animals, such that those individuals that are born are collective improvements on their ancestors. Those individuals, collectively, then provide the genetic base that will improve their descendants, and so on.
As breeding is about improving populations, it makes sense to take our understanding of Mendelian inheritance at an individual level and apply that knowledge to a population. A scaling-up if you will! Population genetics is thus the study of the frequency of genes and genotypes within a population, and how these may change or be maintained through generations.
The latter part of the Background Information section of this blog touched briefly on selection and mating processes. The Selection Process determines which animals get to become parents at all, so as to pass their genes on to the next generation. The Mating Process determines which selected males cover which selected females for any of several end-goals in mind.
The ultimate aim in breeding is to improve a population of animals by taking what makes them ‘best’ in their generation, and amplifying that in the next generation, such that each successive generation contains a greater number each time of animals that are ‘best’.
For numbers of ‘best’ to increase, the frequency of the genes within a population that make it ‘best’ must also increase. Individual animals with the greater number of ‘best’ genes, and which are able to pass those genes on, have a better breeding value as they can improve the population better than the ones that don’t.
Understanding population genetics leads to informed and improved selection and mating systems — the very foundation of good animal breeding. The following posts in this Population Genetics section will discuss gene and genotypic frequencies, and how selection and mating systems can affect those frequencies.