This document discusses dominant gene action in fish breeding. It aims to teach students about basic genetic concepts like gene inheritance, genotype and phenotype. Dominant gene action means that a dominant allele will be expressed in the physical characteristics of an organism regardless of the paired allele. There are three possible genotypes when considering dominant gene action: homozygous dominant, heterozygous and homozygous recessive. However, there are only two possible phenotypes - the dominant phenotype which occurs in homozygous dominant and heterozygous genotypes, and the recessive phenotype which occurs in homozygous recessive genotypes. Punnett squares are used to determine how gene action and inheritance of traits occurs between parents and offspring.