Describe how mRNA is produced in the nucleus of a cell (6 marks)

First, read the question carefully. It asks us to ‘Describe how mRNA is produced’, a good way to approach this is to go through the process step by step. Notice that the question is worth 6 marks, so we need at least 6 pieces of information for a complete answer.

(1) An enzyme called DNA helicase unzips the two strands of DNA by breaking hydrogen bonds between the DNA bases. (2) One strand of DNA acts as the ‘template strand’ and is used to make the mRNA. (3) Free RNA nucleotides bind to the exposed template strand to form the mRNA. (4) Each base binds with its complementary pair: Cytosine (C) – Guanine (G) or G – C , Thymine (T) – Adenine (A), A – Uracil (U) (note a key difference between mRNA and DNA, mRNA has the base U instead of T).  (5) An enzyme called RNA polymerase joins together the bases as they are added. (6) Regions of the mRNA which do not code for genes, called introns, are cut out by a process called splicing to make the final mRNA which leaves the nucleus.