mRNA Processing in Eukaryotes Flashcards
Where are the leader and trailer sequences found during protein synthesis?
On pre-mRNA strands.
Where does translation occur on an mRNA strand?
End of leader sequence to the start of the trailer sequence.
What does UTR stand for?
Untranslated region
What are the regulatory elements?
- Promoter regions
- Enhancer regions
What is an enhancer region in eukaryotes?
Region of DNA that are bound by proteins. These proteins increase likelihood of transcription occurring. These are called transcription factors.
Outline the mRNA cycle
- Transcription synthesizes pre-mRNA
- RNA is processed into mature mRNA
- Transported to cytoplasm
- mRNA works in conjunction with ribosomes to form AA chains
- This is translation
Role of RNA polymerase
Synthesize polymers of nucleic acids.
Enzyme
How many types of RNA polymerase do eukaryotes use?
3 types
- Type I - synthesises ribosomal RNA
- Type II - transcribes to form pre-mRNA
- Type III synthesises tRNA and small nuclear RNAs.
Where do regulatory elements usually reside in DNA?
Normally upstream (sequences involved in regulation)
- TATA box
- CAAT box
- GC box
Three main types of upstrewam regulatory elements (boxes)
What allows molecules to specify whrere the transcription should start on the DNA strand?
The promoter boxes
What does Goldberg-Hogness refer to?
The TATA box.
Surnames of the scientists that discovered it.
-30 position in multicellular eukaryotes
Position of the TATA box.
-75 position is occupied by…
the CAAT box.
Mutation causes big reduction in transcription rate
Does mutation of TATA box affect level of transcription?
No, but does change initiation point.
Does RNA splicing occur in prokaryotes?
NO, this only occurs in eukaryotes.
Role of 5’ cap?
Protect new RNA from degradation and helps to bind to ribosome for translation.
Addition of ~200 adenine bases at end of pre-mRNA.
Poly(A) tail
Not coded by DNA
Helps to stabilize mRNA against degradation
What are introns?
Sequences of RNA on the mRNA which are found in the protein coding sequence that are spliced out of the mature RNA. These regions are not expressed and are not translated.
