Transcription - Lecture 6 Flashcards
What is Transcription?
TRANSCRIPTION is the process of making a copy of genetic information stored in a DNA strand into a completemary strand of mRNA with the air of RNA polymerase .
What are the three steps of Transcription?
Initiation
Elongation
Termination
What occurs in the initation of Transcription?
RNA polymerase binding
DNA chain separation
Transcription Initiation
What occurs in the Elongation phase of transcription?
RNA polymerase and Transcription factor move along the DNA
Addition of mRNA
Rewinding of DNA as the RNA and Transcription factor moves past
What occurs in the Termination phase of transcription?
Release of the final finished chain of mRNA (Transcript)
Where does Transcription begin?
Transcription starts at Nucleotide + 1
Where does RNA polymerase bind on the gene?
Binds to the Promoter region
- Very specific sequence of nucleotides within the DNA
What is the TATA box?
The TATA box is found in all promoters
It is recognised by Pol II
It tells Poll II to start transcribing and in what direction
What RNA Polymerase is stimulated by the TATA box?
Pol II
What is the Tata Binding Protein?
This is a protein that recognises the TATA box and forms a landing platform for all other transcription factors
What is a general transcription factor required for all transcription reactions involving Pol II?
TFIID (TF2D)
What helps determine the transcriptional start and direction for Pol II?
TF2D introduces a kink into the DNA
What starts Transcription initiation?
Require additional General Transcription Factors
TF2D remains at the promoter region for new initiation complexes to form
What allows transcription at low basal rates?
TF2D remains at the a promoter region for initiation of new complexes to form
What direction is the RNA chain synthesised ?
5’ - 3’
How does termination occur?
Newly synthesised RNA makes a stem-loop structure
An enzyme cleaves the RNA off
How is Transcription regulated?
By the use of:
Enhancers
Silences
How is gene expression controlled ?
A regulatory protein can switch on expression of genes
What happens to the Pre-mRNA strand?
Modified by splicing
Introns are spliced out
What is the process of splicing?
Non-coding regions of mRNA are removed (Introns)
Coding regions only left (Exons)
What is an Exon ?
A coding region of DNA
What are introns?
Non-coding regions of DNA
How are the mRNA ends modified?
Addition of a Poly A Tail
Addition of a 5’ cap
What does a Poly A Tail do?
Required for cellular Transport
Stabilises transcription
What does the 5’ cap do?
Protects against degradation
Initiation of Translation
