Transcription Flashcards
What is the order of processes to make a protein?
DNA –> transcription –> mRNA –> translation –> protein
Which strand of DNA is transcribed and why?
Want the RNA molecule to carry the ‘coding information’, so use the non-coding/ template strand to synthesise RNA (3’ –> 5’)
What is a coding sequence?
Portion of a gene’s DNA that is translated into a protein
What is a promotor?
DNA segment recognised by RNA polymerase to initiate transcription, Very AT base rich as it is easier to seperate strands that only have two hydrogen bonds.
What are the 5’ UTR and 3’ UTR sequences?
Untranslated regions that contain regulatory elements that influence on gene expression at the transcriptional and/or translation level By influencing: - mRNA stability - Translation efficiency - Localisation
What is a 5’ G cap?
A specially modified nucleotide that prevents mRNA degradation and regulates translation. By providing: - Ribosome recognition - Binding site Also regulates nuclear export
What is a pol-A tail?
Protects mRNA molecule from enzymatic degradation in the cytoplasm and aids in transcription termination, export of the mRNA from the nucleus, and translation.
What is gene splicing?
The “coding sequence” is not continuous, it is a disrupted sequence
- The mRNA will initially contain intron. Have to remove the intronic sequences then can get a continuous coding sequence
(precursor mRNA –> mature mRNA)
What happens in initiation of transcription?
- Transcription factors bind to the TATA box and other regions of the promotor.
- RNA polymerase 2 binds, forming a transcriptional initiation complex together with the transcription factors
- Proteins guide RNA pol to the starting position at the gene - The two DNA strands separate and RNA polymerase 2 starts mRNA synthesis without the need of a primer
What is a transcription factor?
Are proteins that help turn specific genes on and off by binding to nearby DNA
Why does RNA pol not need a primer?
It can make its own primer. It has an internal 3’ OH group that it can use.
What happens during elongation of transcription?
RNA pol 2 uses the template strand, which runs in the 3’ to 5’ direction as a template and inserts complementary RNA nucleotides in the 5’ to 3’ direction.
What happens in termination of transcription?
The transcription stops at a particular signal
How big of a region of DNA is usually opened up in transcription?
Not big - only around 10-20 bases.
