Mutant An organism that is the result of mutation. Natural selection Change in populations caused by the selection pressure of a changing environment. Certain individuals may have an adaptive advantage and therefore be reproductively fitter. Nicking Special combining ability of some breeds in crosses, or of some pairs of individuals when mated together. A frequency distribution describing the frequency of types varying from the average in a population.
Many biological variables have approximately normal distributions.
Panmixia Random mating. Penetrance Proportion of animals carrying a gene which display the expected characteristic. Complete penetrance occurs when all animals display the expected phenotype. The observed appearance, the sum effect of genetic and environmental influences. Phenotypic correlation Correlation between observed values.