Transcription

Each gene contains a specific nucleotide sequence called the promoter region and it contains the initiation site, where proteins, called transcription factors, and RNA polymerase enzyme recognize and bind to. The enzyme-DNA-protein complex then causes the double helical DNA to unwind from the protective histones and H-bonds between bases break. The DNA in that region separates into its two polynucleotide chains and exposes the sequence of DNA complexes to be copied.
The enzyme then moves along the sequence of DNA until it reaches the initiation site. Translation is initiated and RNA polymerase catalyses the formation of a complementary RNA polynucleotide using the DNA sequence of the template strand as a template. It also ensures that the addition of RNA nucleotides occurs in a 5’ to 3’ direction, systematically, according to complementary base pairing. Hydrogen bonds then form between the base pairs. A and U, C and G, A and T. It also catalyses the formation of phosphodiester bonds when the free RNA nucleotides are added to the 3’ end of the growing nucleotide chain. Upon reaching the end of the gene, it reads the termination sequence and H-bonds between the base pairs will break. The RNA molecule is released from the DNA. Hydrogen bonds then form between the base pairs of the two DNA polynucleotide chains and it rewinds around the protective histones into a double helix again.