Transcription Flashcards
What is transcription?
The process of making RNA from a DNA template
Transcription occurs in the nucleus in eukaryotes.
What are the three phases of transcription?
- Initiation
- Elongation
- Termination
Where is RNA made in eukaryotic cells?
In the nucleus
What is pre-mRNA?
The initial RNA transcript that needs further processing
What does a gene contain?
- A region that codes for RNA
- A promoter
- A terminator
- Regulatory regions
What is the role of the promoter in a gene?
It contains recognition sites for RNA polymerase to bind and control gene expression
What are transcription factors?
Protein complexes required for transcription, usually named TF(something)
What forms the initiation complex during transcription?
Several transcription factors binding to the promoter
What is the transcription bubble?
The region where the DNA strands unwind during transcription
What are the two strands involved in transcription?
- (+) strand (sense or coding strand)
- (-) strand (anti-sense or template strand)
What happens when RNA polymerase reaches the terminator?
The mRNA transcript is complete
What are exons?
Regions in mRNA that code for proteins
What are introns?
Non-coding sections in mRNA that need to be removed
What is intron splicing?
The process of removing introns and joining exons to produce mature mRNA
What is a spliceosome?
A complex made of proteins and RNA that performs intron splicing
What modifications are added to mRNA after transcription?
- 5’-cap
- 3’ poly A tail
What is the purpose of the 5’-cap and 3’ poly A tail?
To prevent mRNA degradation
What are codons?
Three-letter codes formed by nitrogenous bases in mRNA
How many codons are in the genetic code?
64 codons
What do most codons code for?
Specific amino acids
What special codons exist in the genetic code?
- One for ‘start’
- Three for ‘stop’
What is the TATA box?
A sequence located approximately 25-30 bp upstream of the +1 start site that binds the TATA binding protein
What is TFIID?
A multisubunit protein that binds to the TATA box to initiate transcription assembly
What is the role of ATP in transcription initiation?
Energy is provided by the reduction of ATP to ADP and Pi
