Describe how mRNA is formed by transcription in eukaryotes - AQA - A-Level Biology - Question 10 - 2020 - Paper 1

Transcription begins when hydrogen bonds between the bases of the DNA break, allowing for one strand to become accessible as a template.

Only one DNA strand, referred to as the template strand, will serve in the process of transcription.

Free RNA nucleotides then align themselves along the template strand by complementary base pairing, where adenine (A) pairs with uracil (U) rather than thymine (T).

This process is facilitated by the enzyme RNA polymerase, which catalyzes the joining of adjacent RNA nucleotides.

As the RNA polymerase moves along the DNA, it forms phosphodiester bonds between the nucleotides, creating a growing mRNA strand.

After transcription, the primary RNA transcript, called pre-mRNA, undergoes splicing where introns are removed and exons are joined to form mature mRNA, which then exits the nucleus.