Lecture 16: Gene Expression - Transcription Flashcards
What is gene expression?
The process by which information from a gene is used to synthesis functional gene products
What are examples of functional gene products?
- Protein
- Non-coding RNA
What is a gene?
A defined sequence of DNA that produces a type of RNA molecule that has some function
What might a gene be responsible for?
The regulation of RNA synthesis
What is transcription?
DNA-dependant RNA synthesis
What catalyses transcription?
RNA polymerase
What type of RNA is made during transcription?
mRNA
How does RNA polymerase synthesise mRNA?
By catalysing the formation of phosphodiester bonds between ribonucleotides
What does RNA polymerase do during transcription of then catalyse the formation of bonds?
Selects the correct nucleotides to incorporate into mRNA based on the sequence of the DNA being transcribed
What are complementary DNA strands?
Two strands running antiparallel
What are complementary sequences made of?
They are made of one coding strand and one template strand
What direction does the coding strand run?
5’ -> 3’
What direction does the template strand runs in?
3’ -> 5’
What is mRNA transcribed from?
The DNA template strand
What regulates initiation?
Specific DNA sequences
What do transcription factors bind to during initiation?
They bind to the TATA box and other regions of the promoter
What does RNA polymerase II do during initiation?
binds forming a transcription initiation complex with transcription factors
After DNA strands seperate during initiation what do DNA polymerase II do?
start synthesising mRNA without the need of the a primer
What does the RNA polymerase II do during elongation?
It starts to insert complementary RNA nucleotides in the 5’ -> 3’ direction
Where does transcription occur?
In the nucleus
Where does translation occur?
In the cytoplasm
What are introns?
Non-coding regions
What are exons?
Coding regions
What do 5’ UnTranslated Regions (UTR’s) facilitate?
The addition of of the 5’ G cap
What do 3’ UnTranslated Regions (UTR’s) facilitate?
The addition of the polyA tail
What does a poly-A tail do?
It prevents mRNA degeneration and facilitate mRNA export from the nucleus
