Transcription Flashcards
What is gene expression?
Gene expression is the process in which information from a gene is used in the synthesis of a functional gene product: protein or non coding RNA
What is transcription?
DNA dependent RNA synthesis catalysed by the enzyme RNA polymerase. RNA polymerase synthesises mRNA by catalysing the formation of phosphodiester bonds between ribonucleotides. RNA polymerase selects the correct nucleotides to incorporate into mRNA based on the sequence of DNA which is being transcribed.
Which DNA strand is transcribed?
mRNA is transcribed from the template strand : 3’ ——> 5’
What are the three stages of transcription?
- Initiation
- Elongation
- Termination
What is initiation?
(TRANSCRIPTION)
- Transcription factors bind to the TATA box and other regions of promoter
- RNA pol II binds forming a transcriptional initiation complex together with the transcription factors
- The two DNA strands seperate and RNA pol II starts, mRNA synthesis without need of a primer
What is elongation?
(TRANSCRIPTION)
RNA pol II uses the template strand, which runs in the 3’ —> 5’ direction as a template and inserts complementary RNA nucleotides in the 5’ —> 3’ direction
What is the coding sequence?
(Transcription)
Portion of a genes DNA that is translated into a protein
What is a promoter?
(Transcription)
DNA segment recognised by RNA polymerase to initiate transcription
What are UTRS (untranslated region)?
(Transcription)
Transcribed but not usually translated, contain regulatory elements that influence gene expression
5’ UTR facilitates addition of the 5’ G Cap
3’ UTR facilitates addition of the polyA tail
What is a 5’ G cap?
(Transcription)
Prevents mRNA degrading, promotes intron excision and provides a binding site for the small ribosomal unit
What is Poly-A tail?
(Transcription)
Prevents mRNA degradation and facilitates export of the mRNA from the nucleus to the cytoplasm
