DNA structure. Three-dimensional model of the double helix. Implications of the DNA structure: denaturation, hybridization, DNA-protein interaction. Mechanism of replication and enzymes involved. Telomeres and telomerase. Versatility of RNA. Modified bases. Three-dimensional conformations of single stranded RNA. The genetic code. Transcription. RNA Polymerase: holoenzyme and sigma factor. Promoter sequences. Initiation, elongation, termination of transcription. The Lac operon. The processes of RNA modification. Eukaryotic mRNA maturation. Splicing mechanisms. Classes of RNA. Activation of tRNA. The ribosome. The mechanism of protein synthesis. Initiation, elongation and termination in prokaryotes. The Principle of PCR.