Central dogma

The central dogma refers to the flow of genetic information: DNA →transcription→ RNA →translation→ Protein; and DNA → replication → DNA. Polynucleotide synthesis (transcription and replication) in all cells proceeds in the 5’ - 3’ direction for both RNA and DNA. This is because the precursors are 5’-nucloeside triphosphates and the free 5'-phosphate is subjected to a nucleophilic attack by the 3’-OH group of the growing polynucleotide chain.