Unit 3 Revision Flashcards
What is transcription? Where does it occur?
Transcription is the process where the DNA sequence is copied and converted to an mRNA molecule.
It occurs in the nucleus.
What happens to the pre-mRNA strand before it leaves the nucleus?
The mRNA strand must undergo RNA processing.
A methyl cap is added to the 5’ end and a poly-A tail is added to the 3’ end. The secures and protects the mRNA when it leaves the nucleus.
The strand contains coding (exons) and non-coding (introns) regions. The introns getting removed and the exons get spliced together.
What are the steps of transcription?
First DNA unwinds. The 5’ to 3’ strand is the template strand and the 3’ to 5’ strand is the coding strand.
DNA polymerase binds to the template strand at the 5’ end and runs along the strand bringing in complementary nitrogenous bases in a 3’ to 5’ direction. It reads the template strand and builds an pre-mRNA strand that matches the coding strand except Thymine is swapped for Uracil.
