Describe the process of transcription

Transcription is the first step in gene expression that copies a DNA molecule into an RNA molecule (transcript). Such RNA molecules can either be mRNAs, if the gene that is transcribed is protein coding, or regulatory RNAs that carry out specific roles in the cells. The mRNAs serve as templates for protein synthesis in the process called translation, carried out in the cytoplasm. Hence, transcription is the first important step that carries genetic information from DNA to RNA, and ultimately proteins. Transcription is an enzymatic process, catalysed by an enzyme called RNA polymerase that can generate an RNA molecule using the DNA molecule as a template. Additional proteins termed transcription factors are also involved, which regulate the process. Transcription is carried out in three main steps: initiation, elongation and termination. During initiation, initiation factors bind to the promoter of a gene and additional DNA sequences, allowing recruitment of RNA polymerase. The DNA strands become locally unwound, and the RNA polymerase starts generating the RNA molecule by adding ribonucleotides, which are complementary to the nucleotides of the DNA template, into the growing RNA chain. The complementary bases are adenine-uracil and guanine-cytosine (uracil replaces thymine in RNA). During elongation, the transcript is quickly synthesised upon which transcription is terminated and the RNA polymerase as well as the transcript are released. Such transcript will, as mentioned above, either carry out specific functions in the cell or serve as a template for protein synthesis.