| Sumario: | Genetics (from Ancient Greek yEVETIKóç genetikos, "genitive" and that from yéveo genesis, "origin"), a discipline of biology, is the science of genes, heredity, and variation in living organisms. Genetics deals with the molecular structure and function of genes, with gene behavior in the context of a cell or organism (e.g. dominance and epigenetics), with patterns of inheritance from parent to offspring, and with gene distribution, variation and change in populations. Given that genes are universal to living organisms, genetics can be applied to the study of any living system from viruses and bacteria, through plants (especially crops) to humans (for example in Medical Genetics) The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding. However, the modern science of genetics, which seeks to understand the process of inheritance, only began with the work of Gregor Mendel in the mid-19th century. Although he did not know the physical basis for heredity, Mendel observed that organisms inherit traits via discrete units of inheritance, which are now called genes. Genes correspond to regions within DNA, a molecule composed of a chain of four different types of nucleotides - the sequence of these nucleotides is the genetic information organisms inherit. DNA naturally occurs in a double stranded form, with nucleotides on each strand complementary to each other. Each strand can act as template for creating a new partner strand -- this is the physical method for making copies of a genes that can be inherited.
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