Farmers long ago noted that they coud improve each year's harvest by using seed from only the best plants of the current crop Plants that,for example,gave the highest yield,stayed the healthiest during periods of drought or disease.or were easiest to harvest tended to produce future generations with these same characteristics.Through several years of careful seed selection.farmers could maintain and strengthen such desirable traits. The possibilities for improving plants expanded as a result of Gregor Mendel's investigations in the mid-1860s of hereditary traits in peas.Once the genetic basis of heredity was understood,the benefitsof cross-breeding.or hybridization,became apparent:plants with different desirable traits could be used to cultivate a later generation that combined these characteristics. An understanding of the scientific principles behind fermentation and crop improvement practices has come only in the last hundred years.But the early,crude techniques,even without the benefit of sophisticated laboratories and automated equipment,were a true practice of bitechnology guiding natural processes to improve man's physical and economic well-being Harnessing Microbes for Health Every student of chemistry knows the shape of a Buchner funnel,but they may be unaware that the distinguished German ientist it was named after made the vital discovery (in 1897)that enzymes extracted from yeast are effective in converting sugar into alcohol.Major outbreaks of disease in overerowded industrial cities led eventually to the introduction,in the early years of the present century, of large-scale sewage purification systems based on microbial activity.By this time it had proved possible to generate certain key industrial chemicals(glycerol,acetone,and butanol)using bacteria. Another major beneficial legacy of early 20th century biotechnology was the discovery by Alexander Fleming (in 1928)of penicillin,an antibiotic derived from the mold Penicillium.Large-scale production of penicillin was achieved in the 1940s.However,the revolution in understanding the chemical basis of cell function that stemmed from the post-war emergence of molecular biology was still to come.It was this exciting phase of bioscience that led to the recent explosive development of biotechnology. 4 4 Farmers long ago noted that they could improve each succeeding year's harvest by using seed from only the best plants of the current crop. Plants that, for example, gave the highest yield, stayed the healthiest during periods of drought or disease, or were easiest to harvest tended to produce future generations with these same characteristics. Through several years of careful seed selection, farmers could maintain and strengthen such desirable traits. The possibilities for improving plants expanded as a result of Gregor Mendel's investigations in the mid-1860s of hereditary traits in peas. Once the genetic basis of heredity was understood, the benefits of cross-breeding, or hybridization, became apparent: plants with different desirable traits could be used to cultivate a later generation that combined these characteristics. An understanding of the scientific principles behind fermentation and crop improvement practices has come only in the last hundred years. But the early, crude techniques, even without the benefit of sophisticated laboratories and automated equipment, were a true practice of biotechnology guiding natural processes to improve man's physical and economic well-being. Harnessing Microbes for Health Every student of chemistry knows the shape of a Buchner funnel, but they may be unaware that the distinguished German scientist it was named after made the vital discovery (in 1897) that enzymes extracted from yeast are effective in converting sugar into alcohol. Major outbreaks of disease in overcrowded industrial cities led eventually to the introduction, in the early years of the present century, of large-scale sewage purification systems based on microbial activity. By this time it had proved possible to generate certain key industrial chemicals (glycerol, acetone, and butanol) using bacteria. Another major beneficial legacy of early 20th century biotechnology was the discovery by Alexander Fleming (in 1928) of penicillin, an antibiotic derived from the mold Penicillium. Large-scale production of penicillin was achieved in the 1940s. However, the revolution in understanding the chemical basis of cell function that stemmed from the post-war emergence of molecular biology was still to come. It was this exciting phase of bioscience that led to the recent explosive development of biotechnology