This chapter discusses the origin of genetics, and describes simple Mendelian genetics. Two important concepts in development and genetics are epigenesis and epigenetics. Epigenesis is a school of thought that maintains that the developing organism gradually comes into existence. The chapter explains how genes are transmitted from parents to offspring is the task of the geneticist. The sequence of the deoxyribonucleotides encodes information, genetic information, which, among other things, provides instructions for the development of the embryo and fetus. Translation process involves the conversion of the information in a sequence of ribonucleotides in a mRNA molecule to information in a sequence of amino acids in a protein molecule. The chapter explores the importance of cytogenetics and chromosomes in human development, and describes the roles of deoxyribonucleic acid replication, transcription, and translation in human development. Banding of chromosomes allows subtle genetic damage to be picked up.