This paper presents an activity that engages students in model-based reasoning, requiring them to predict the behavior of the trp and lac operons under different environmental conditions. Students are presented six scenarios for the "trp" operon and five for the "lac" operon. In most of the scenarios, specific mutations have…

Describes the rapid advance of molecular genetics over the past 20 years that have accounted for the origin of mutations. This research has revealed that variation within species is much greater than Darwin postulated. (Author/MA)

The development of enzymes as biocatalysts for industrial use and the emergence of directed evolution in the invention of advanced biocatalysts are discussed and illustrated. Thus, directed evolution has bridged the functional gap between natural and specially designed biocatalysts.

Describes the unicellular microorganisms of three billion years ago. Explains how these primitive cells gave rise to biochemical systems and the present oxygen-rich atmosphere. Numerous diagrams, charts, and illustrations. (MA)

Presents various ideas on the origin of life including very early ideas, Oparin's view, and an alternative view related to carbonaceous chondrites. Outlines one currently tenable hypothesis in the formation of the solar system and explains the method involved in detecting polyatomic molecules in dark nebulae. (GS)

Describes the Miller and Urey experiment to synthesize organic compounds. Includes subsequent research and relates these studies to the formation of one-celled organisms in an oxygen-free atmosphere. (MA)

Provides an introduction to the field of molecular evolution. Changes in genetic material and proteins help to time the stages of species evolution. (BB)

Osmotic aspects of aqueous solutions that are usually disregarded in biochemistry textbooks are presented. This article discusses the osmolarity of seawater, evolution of organisms over geological time, ionic adaptation of cells, ionic concentrations in bacteria, osmolytes and blood electrolytes in water-stressed organisms and land vertebrates,…

Discusses various theories about life on Mars and biochemical experiments pertaining to the origin of life. (MLH)

Presents an evolutionary scheme for the physical, chemical, and biological origins of life. The molecular factor is the field of analysis. The need for a reconciliation of science and philosophy is indicated. Extensive references are given. (MA)

Described is thin-layer chromatography (TLC), a technique that can be conveniently used in the laboratory to generate evidence supporting the principle that degrees of biochemical similarity reflect degrees of evolutionary relatedness among organisms. (Author/PEB)

Relates occurrences at the Asilomar conference that led to the drafting of guidelines for gene-transplant research. The guidelines allow some experiments, defer others until safer containment is available, and ban those considered highly dangerous. (GS)

Discusses the relation between amino acids and ribonucleic acid (RNA) in a copolymer. (HM)

Describes current experiments that help to explain chemical processes which probably existed prior to the first living cells. Some experiments suggest that a significant portion of a major metabolic pathway, the Krebs cycle, may have developed in the earth's primitive atmosphere to be later incorporated into living organisms. (JR)

Outlines the proteinoid theory of the origin of life and examines competing or alternative concepts in the light of a sequential experimental model. (JR)