Explain how mRNA is formed. (6 marks)

DNA helicase breaks the hydrogen bonds between the base pairs in the double-stranded DNA. RNA nucleotides then line up beside their corresponding nitrogenous base (A-T, C-G) along the template strand of the DNA (only one of the DNA strands acts as the template). RNA polymerase joins the RNA nucleotides together via condensation reactions that result in the formation of the phosphodiester bonds. Pre-mRNA is then spliced to remove introns before it is ready for translation.