Genetics is a fundamental course of the first year of the degree in Biology. It begins with the Mendelian inheritance and its extensions (theory and exercises). The extension of the Mendelian view of the gene to the modern view - the gene as a unit of transcription - is the central part of the course. Thus, the structure and organization of the genetic material, and its expression through replication, transcription and translation, are exhaustively presented. Regulation of gene expression in prokaryotes as well as in eukaryotes is explained in detail. The process of mutation in genes, chromosomes and genomes allows for an adequate understanding of the evolution of the genetic material. The last part of the course relies on the genetics of populations and the genetics of quantitative traits, with particular emphasis to the origin, maintenance and significance of the genetic variability. Finally, a few lessons concern the evolutionary genetics at the molecular level (DNA and protein sequence analysis with bioinformatics tools).