Describe the process of transcription of DNA

DNA transcription is the process of copying the DNA strand in order to make mRNA that is needed for protein synthesis. Firstly, RNA polymerase attaches to the double helix of DNA, this unwound by the RNA polymerase enzyme. Free RNA nucleotides then line up against the single DNA chains using the base pairing rule - cytosine to guanine, adenosine to thymine. However in RNA, the thymine is replaced by uracil, therefore, uracil will line up against adenosine in place of thymine.

To form the mRNA strand, the sugar-phosphate backbone of the free RNA nucleotides must form. This is also completed by the RNA polymerase that runs down the strand. mRNA is then formed and is able to leave the nucleus through the nuclear pores in the nuclear envelope. DNA will then reform its hydrogen bonds and rewind into the helical shape.