Biochemistry [antikvár]

PREFACE to the Third Edition Biochemistry has been profoundly transformed by recombinant DNA technology. The genome is now an open book—any passage can be read. The cloning and sequencing of millions of bases of DNA have greatly enriched our understanding of genes and proteins. Indeed, recombinant DNA technology has led to the integration of molecular genetics and protein chemistry. The intricate interplay of genotype and phenotype is now being unraveled at the molecular level. One of the fruits of this harvest is insight into how the genome is organized and its expression is controlled. The molecular circuitry of growth and devel-opment is coming into view. The reading of the genome is alsó provid-ing a wealth of aminő acid sequence information that illuminates the entire protein landscape. Scarce proteins can be produced in abun-dance by transfected cells. Moreover, precisely designed növel proteins can be generated by site-specific mutagenesis to elucidate how proteins fold, catalyze reactions, transduce signals, transport ions, and intercon-vert different forms of free energy. Our understanding of molecular evolution alsó has been greatly enriched by the recombinant DNA revolution. Families and superfamilies of proteins have come into view. Theme and variadon at the level of proteins are vivid expressions of the underlying processes of gene du-plication and divergence. The genes of complex proteins display the coming together in evolution of exons encoding functional modules. The many recurring structural and mechanistic motifs seen throughout nature testify to the fundamental unity of all forms of life. The discov-ery of catalytic RNA enables us to envision an RNA world early in the evolution of life, prior to the appearance of DNA and protein. The ubiquity of ribonucleotides in metabolism and the central roles played