L4: Translation Process Flashcards
What are the 3 sections which make up the structure of mRNA?
- Promoter = transcriptional start site
- Coding region = transcript
- Terminator = Non-transcribed section of the region but ensure fidelity and protection of the transcribed coding region
What is the coding region made up of?
Exons and introns
What elements are found towards the 5’ end region of the promoter?
Upstream enhancers
Define upstream enhancers
A short (50-150 bp) region of DNA that can be bound to proteins, important activators to the transcription of a particular gene
Where are upstream enhancers located in terms of the coding gene?
- Sequences of DNA that can be several thousand kilo bases away from the promoter it is enhancing
- Far away in terms of base pairs that may intervene and enhance the promoter
How does the DNA double helix benefit the upstream enhancers?
Structure allows the enhancers to be bought closer (compact structure) to the promoters
Define promoter
- A regulatory region of DNA located upstream (towards the 5’ end) of a gene, providing a control point for regulated gene transcription
- Control and regulate gene expression
What is a TATA box?
- In the promoter region, these are a sequence of DNA that spell out TATA
- These can be a sequence like TATA or TAATA, or a string of letters that run together to make a TATA box
Define TATA box
A sequence of DNA, consisting of nucleobases TATAAA, located in the promoter region about 25-30 base pairs before the transcription start site
Can a gene be without a TATA box?
Yes
Some genes don’t have a TATA box, but have a specific motif that will allow the transcriptional machinery to identify that the region is important and needs to be transcribed
What is located before the first exon on the coding gene?
Towards the 5’ end is a sequence known as the untranscribed region (UTR)
What is an untranscribed region (UTR)?
Part of the DNA and gene, but not transcribed. Acts as a protector for the genome
What is located after the last exon in the coding gene?
- At the 3’ end is another untranscribed region (UTR)
- This acts as an insulator to protect the genome
What proteins does RNA polymerase require to aid in the process of transcription?
- TATA box = 25-30bp away from the transcription start site (TSS). TATAA n GCCC
- CCAAT box = 100 bp away from the TSS. TAGCCAATG
- GC box = 200 bp away from the TSS. ATAGGCGnGA
What structures make up mRNA?
From the 5’ to 3’ end
Leader, Reading frame, Trailer
What are UTRs in mRNA? Where are they found?
Untranslated regions
The UTRs are transcribed but not translated
Found in the leader and trailer regions of the mRNA sequence
Why does mRNA always vary in length?
Sequences of mRNA vary because amino acid coding sequences (reading frames) vary, and it depends on which reading frame is open and because leader and trailer sequences differ
Using the real example below, identify the reading frame, and the leader and trailer sequences of the sequence of mRNA:
5’ UACCAUGGCACUGGUCGAUCAUAAAGGGGGUCGAUGACC 3’
- No 3rd reading frame as there is no AUG start codon - no N-Met
- 2nd reading frame selected as there is a start and stop codon (AUG and UGA)
- Leader sequence at the 5’ end is U ACC (before TSS)
- Trailer sequence at the 3’ end is CC (after the transcript)
- All keeps an integral gene which can function