1 Introduction.- 2 The structure of the nucleic acids.- 3 Genomes of eukaryotes, bacteria and viruses: chromosome organization.- 4 Degradation and modification of nucleic acids.- 5 The metabolism of nucleotides.- 6 Replication of DNA.- 7 Repair, recombination and rearrangement of DNA.- 8 The arrangement of genes.- 9 RNA biosynthesis.- 10 Control of transcription.- 11 Processing of RNA transcripts and its control.- 12 The translation of mRNA: protein synthesis.- Appendix: methods of studying nucleic acids.- A.1 Occurrence and chemical analysis.- A.1.1 Chemical determination of nucleic acids in tissues.- A.1.2 Analysis of base composition and nearest-neighbour frequency.- A.1.3 Estimation of the molecular weight of DNA.- A.2 Isolation and separation of nucleic acids.- A.2.1 Isolation and separation of DNA.- A.2.2 Isolation and separation of RNA.- A.3 Hybridization of nucleic acids.- A.4 Methods of labelling nucleic acids.- A.4.1 General labelling methods.- A.4.2 End-labelling methods.- A.5 Determination of nucleic acid sequences.- A.5.1 Determination of DNA sequences.- A.5.2 Determination of RNA sequences.- A.6 Restriction mapping of DNA.- A.7 The polymerase chain reaction.- A.8 Cloning DNA.- A.8.1 The principles.- A.8.2 The major cloning vectors.- A.8.3 cDNA cloning.- A.8.4 Genomic cloning.- A.9 Analysis and manipulation of cloned DNA.- A.9.1 Mapping of RNA transcripts.- A.9.2 Identification of regions of DNA that interact with proteins.- A.9.3 Expression.- A.10 Chemical synthesis of oligonucleotides.- A.11 Cell-free systems for transcription and translation.- A.12 The use of inhibitors in the study of gene expression.- References.