Transcription

Key Notes

What You Will Learn

• Definition of transcription

• Steps in the transcription process

• How transcribed mRNA is processed in eukaryotes

What is Transcription?

• Transcription is the process of copying genetic information from DNA to RNA

• It is the first step of protein synthesis and occurs in the nucleus of eukaryotic cells

• The result is mRNA, which carries genetic instructions to the ribosome for translation

Steps of Transcription

1. Initiation – RNA polymerase binds to the promoter region, unwinding DNA

2. Elongation – RNA polymerase adds complementary RNA nucleotides to form the mRNA strand

3. Termination – Transcription stops when RNA polymerase reaches a stop sequence, and mRNA detaches

Processing of mRNA in Eukaryotes

• Splicing – Removes introns (non-coding regions) and joins exons (coding regions)

• Editing – Modifies nucleotides to create different protein forms

• Polyadenylation – Adds a poly-A tail (string of adenine bases) to protect mRNA and aid in export from the nucleus

Summary

• Transcription follows the DNA → RNA flow of genetic information

• Takes place in the nucleus and produces a complementary mRNA strand

• In eukaryotes, mRNA undergoes processing before leaving the nucleus