gene expression Flashcards
(15 cards)
What is the process of producing a complementary RNA from a gene called?
Transcription
Transcription involves the enzyme RNA polymerase and results in a temporary DNA-RNA hybrid.
What type of strand of DNA is copied to produce a complementary RNA during transcription?
Anti-sense strand
The anti-sense strand is the template for producing sense RNA.
How many RNA polymerases do bacteria and eukaryotes have?
Bacteria have one, eukaryotes have three
This reflects the complexity of transcription in eukaryotic cells.
What is the shape of RNA polymerases?
Claw shape
The active site is located at the base in the ‘active site cleft’.
What are the three types of eukaryotic RNA polymerases and their functions?
- RNA polymerase I: transcribes large rRNA precursor genes
- RNA polymerase II: transcribes all protein-encoding genes
- RNA polymerase III: transcribes tRNA genes, snRNA genes, and 5S rRNA genes
Each type of RNA polymerase has specific roles in gene expression.
List the three phases of the transcription cycle.
- Initiation
- Elongation
- Termination
These phases describe the process through which transcription occurs.
What occurs during the initiation phase of transcription?
RNA polymerase binds to the gene promoter
This binding leads to unwinding of the DNA.
What is the transcription bubble?
A short stretch of double-stranded DNA (14bp) that is opened by RNA polymerase
This allows the anti-sense template strand to be copied.
What are the two types of transcription termination in prokaryotes?
- Rho-independent
- Rho-dependent
Rho-independent involves a hairpin structure, while Rho-dependent requires a specific termination factor.
What is the role of the TBP in eukaryotic transcription initiation?
TBP binds to the TATA box
This is crucial for the recruitment of RNA polymerase II.
Fill in the blank: The ‘allosteric’ model of transcription termination involves recognition of the processing site and RNA cleavage producing a _______ in the polymerase.
conformational change
This change leads to the release of the polymerase from the template.
What does RNA polymerase catalyze during transcription?
Formation of phosphodiester bonds between ribonucleotides
This is essential for building the RNA strand.
What is a promoter in the context of transcription?
The DNA sequence to which RNA polymerase binds to begin transcription
Promoters are key regulatory elements in gene expression.
What happens during the elongation phase of transcription?
RNA polymerase progresses along the gene
This phase is where the RNA strand is extended.
What is the termination event in transcription?
The polymerase stops and releases the RNA product
This marks the end of the transcription cycle.
