# Explain how transcription produces a messenger RNA (mRNA) molecule from a DNA template strand.

> IB DP Biology Standard Level (2023 syllabus) — D1.2 Protein synthesis · Explain · 4 marks

## Mark scheme (4 marks)

1. RNA polymerase binds to the promoter region of the DNA and unwinds / unzips the double helix by breaking hydrogen bonds between complementary base pairs
2. RNA polymerase moves along the template (antisense) strand in the 3′ to 5′ direction, reading the exposed bases
3. Free RNA nucleotides are added by complementary base pairing to the template strand, with uracil (U) pairing with adenine (A) instead of thymine
4. RNA polymerase joins the RNA nucleotides by forming phosphodiester bonds, elongating the mRNA in the 5′ to 3′ direction, until a termination sequence is reached and the mRNA is released

## Key terms

- [transcription](https://www.gradenine.co.uk/glossary/transcription)
- [template strand](https://www.gradenine.co.uk/glossary/template-strand)
- [mRNA](https://www.gradenine.co.uk/glossary/mrna)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-transcription-produces-a-messenger-45797a21) · Published by Druglandscape Ltd.