Genetic engineering : DNA and The Human Genome

 Genetic engineering : DNA and The Human   Genome
                     By the mid- to late twentieth century, two more break through took place that gave scientists a greatly improved understanding of genes and how they work. First, scientists discovered the structure of the fundamental molecule that provides the key to the hereditary process—deoxyribonucleic acid (DNA). The other involved the location and identification of all the genes—the full set of genetic instructions—found in human cells.

                     In 1909, Danish botanist Wilhelm Johann-sen (1 857—I 927) came up with the term gene to describe the idea of “hereditary elements.” By the early 1950 s two American geneticists, Alfred Hershey and Martha Chase, discovered that the molecule known as DNA carried the genetic information that is passed on from a parent cell to its offspring—or from a parent organism to its offspring. By 1953, two scientists working in Britain—American biochemist James Watson and British biophysicist Francis Crick—discovered the structure of DNA, a twin spiral called a “double hel ix.” This led to a burst of growth in molecular biology— the study of the molecules that make up living things.

                    A few years later a Swiss microbiologist named Warner Ar her found an enzyme that marked the boundaries of each gene along a strand of DNA. That discovery made the next step possible. In 1973, two American biochemists, Stanley Cohen and Herbert Boyer, used Ar ber’s discovery to locate a specific gene in a bacterium, remove it, and place it in another bacterium. This process became known as recombinant DNA technology, or gene splicing, and it was the beginning of genetic engineering.