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

The process begins with the breaking of hydrogen bonds between the DNA bases, thereby unwinding the double helix structure.

Only one of the DNA strands serves as the template for mRNA synthesis.

Free RNA nucleotides in the nucleus align with the exposed DNA bases through complementary base pairing. Specifically, adenine pairs with uracil, while cytosine pairs with guanine.

RNA polymerase, the enzyme responsible for transcription, catalyzes the joining of these RNA nucleotides, forming a growing mRNA strand.

As RNA polymerase moves along the template DNA strand, it facilitates the formation of phosphodiester bonds between the adjacent nucleotides, further elongating the mRNA molecule.

Once the entire gene is transcribed, the resulting pre-mRNA undergoes processing, where introns are removed, and exons are spliced together to form the final mRNA.

The final mRNA strand then exits the nucleus through the nuclear pores, ready for translation.