Introduction
Quantitative Genetics is that branch of Population Genetics which deals with phenotypes which vary continuously, and are best dealt with using Statistics (Biometrics). The phenotypes and underlying genotypes are summarised by measures of Central Tendency (e.g. the Mean) and Variability (e.g. the Variance). Unlike other foci of Population Genetics, the phenotypes are not readily classifiable into "classes", of which a census may be ascertained. Some attributes may be analysable either way, depending upon the metric used to quantify them. Mendel himself had to discuss this matter in his famous paper, especially with respect to his attribute "length of stem". Quantitative Genetic analyses are heavily dependant on appropriate population Mating Systems, allowing zygotic frequencies to be specified appropriately from the gametic frequencies giving rise to them. Consequently, it can analyse phenotypic results arising from many situations, such as small mating-groups, gene-"islands", genetic drift, and inbreeding. It can analyse and "explain" heredity in its passage through both space (populations) and time (generations). It allows an understanding of methods used in plant and animal breeding, and of micro-evolution (e.g. Natural Selection).
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