Classical genetics

Classical genetics is the branch of genetics based solely on visible results of reproductive acts. It is the oldest discipline in the field of genetics, going back to the experiments on Mendelian inheritance by Gregor Mendel who made it possible to identify the basic mechanisms of heredity. Subsequently, these mechanisms have been studied and explained at the molecular level. Classical genetics consists of the techniques and methodologies of genetics that were in use before the advent of molecular biology. A key discovery of classical genetics in eukaryotes was genetic linkage. The observation that some genes do not segregate independently at meiosis broke the laws of Mendelian inheritance and provided science with a way to map characteristics to a location on the chromosomes. Linkage maps are still used today, especially in breeding for plant improvement. After the discovery of the genetic code and such tools of cloning as restriction enzymes, the avenues of investigation open to geneticists were greatly broadened. Some classical genetic ideas have been supplanted with the mechanistic understanding brought by molecular discoveries, but many remain intact and in use. Classical genetics is often contrasted with reverse genetics, and aspects of molecular biology are sometimes referred to as molecular genetics. At the base of classical genetics is the concept of a gene, the hereditary factor tied to a particular simple feature (or character). The set of genes for one or more characters possessed by an individual is the genotype. A diploid individual often has two alleles for the determination of a character. Classical genetics is the aspect of genetics concerned solely with the transmission of genetic traits via reproductive acts. Genetics is, generally, the study of genes, genetic variation, and heredity. The process by which characteristics are passed down from parents to their offspring is called heredity. In the sense of classical genetics, variation is known as the lack of resemblance in related individuals and can be categorized as discontinuous or continuous.