Outline of genetics, genetic polymorphisms, allelic and genotypic frequencies, kinship test (paternity, maternity), interaction between genes. Mutations in livestock animals. Genotype/Phenotype. Genotype-environment interaction. Qualitative vs quantitative traits. Heterosis. Traits inheritance. Maternal effect and cytoplasmic heredity. Environmental vs genetic variability. Feline and canine genetics: genes involved in the appearance: coat colours, coat patterns, ear conformation, etc. Genetic improvement in pet’s breeding: genetic improvement vs “genetic abuse”, consequences of excessive selective pressure and genetic isolation, identification of problems and strategies to reduce the incidence of genetic diseases. Heterosis and hybrid vigor vs inbreeding depression. Genetic tests. Templates of genetic improvement for species and for productive attitude. Morphological and genetic evaluation of the candidate reproducers.