Transcription Flashcards
(22 cards)
What is transcription?
The synthesis of RNA from a DNA template
Transcription is a key process in gene expression where RNA is synthesized based on the sequence of DNA.
What enzyme catalyzes transcription?
RNA polymerase
RNA polymerase is essential for synthesizing RNA during transcription.
In which direction is RNA synthesized during transcription?
5’ to 3’
This directionality is crucial for proper RNA synthesis.
What is the role of the anti-sense strand in transcription?
It serves as the template for RNA synthesis
The anti-sense strand is complementary to the newly synthesized RNA.
What are the nitrogen base pairing rules in RNA synthesis?
A-U and C-G
These rules dictate how RNA bases pair with DNA bases during transcription.
What is required for transcription to occur?
ATP, GTP, CTP, and UTP
These nucleotides provide the necessary building blocks for RNA synthesis.
Does RNA synthesis require a primer?
No
Unlike DNA synthesis, RNA synthesis does not require a primer to initiate.
What is a prokaryotic promoter sequence?
A region recognized by RNA polymerase at the 5’ end of genes
Promoters are essential for initiating transcription in prokaryotes.
What is an operon?
A group of genes coding for proteins involved in a common metabolic pathway
Operons allow coordinated expression of related genes in prokaryotes.
What happens to transcription when lactose is absent in the lac operon?
Transcription is repressed
The Lac I repressor binds to the operator, blocking RNA polymerase.
How many types of RNA polymerase are present in eukaryotic cells?
Three
Each RNA polymerase transcribes different types of RNA and recognizes specific promoters.
What are the functions of RNA Pol I, II, and III in eukaryotes?
- RNA Pol I: precursors of rRNAs
- RNA Pol II: mRNA precursors
- RNA Pol III: tRNAs and small RNAs
These polymerases play distinct roles in RNA synthesis.
What is the function of the TATA box in eukaryotic transcription?
It serves as a binding site for transcription factors
The TATA box is critical for the assembly of the transcription initiation complex.
What is backtracking in RNA polymerase?
A mechanism for error correction during transcription
Backtracking allows RNA polymerase to correct mistakes in the RNA transcript.
What is alternative splicing?
A process that allows a single gene to produce multiple protein products
Alternative splicing contributes to the complexity of gene expression.
What is polyadenylation?
The addition of a poly-A tail on the 3’-end of RNA
This process is important for RNA stability and transport in eukaryotes.
True or False: Splicing occurs in both eukaryotes and prokaryotes.
False
Splicing is a process exclusive to eukaryotes.
What is the general error rate of RNA polymerase during transcription?
1 error in 10,000 base pairs
This error rate is higher than that of DNA replication but acceptable due to multiple transcripts being produced.
What do histone-modifying enzymes do?
Make covalent modifications to the histone core octamer
These modifications play a role in regulating gene expression by altering chromatin structure.
What is the ‘histone code’?
Combinatorial modifications of histone tails that regulate gene expression
The histone code is involved in determining whether chromatin is active or inactive.
What are transcription factors?
Proteins that regulate transcription by binding to DNA
Transcription factors often have both DNA-binding and activation/repression domains.
What is a helix-turn-helix motif?
A structural motif in transcription factors that fits across the major groove of DNA
This motif facilitates specific DNA binding by transcription factors.
