Transcription Flashcards
What is the differences between RNA and DNA?
Ribose instead of deoxyribose
Uracil instead of thymine
Single stranded
Name the 5 types of RNA
mRNA rRNA tRNA snRNA miRNA
What is the role of mRNA?
Template for proteins synthesis
What is the role of rRNA?
major compartment of ribosomes
What is the role of tRNA?
carries amino acids in activated form to the ribosomes
Describe RNA Synthesis
RNA produced by copying one strand of DNA
Catalysed by RNA polymerase using rNTPS realising pyrophosphate
NO PRIMER IS NEEDED
Nucleotides added to 3’OH
Describe Transcription initiation
At the start units are marked by promoters that demined the start.
Initiation factor directs the enzymes to the correct initiation site
Core Enzyme alpha 2 Beta Beta’ Omega
Describe Transcription initiation in prokaryotes
Pribnow Box ( AT rich region at -10) TTGACA at -35
Describe the start of Transcription
Binding to template causes DNA separation.
RNA synthesis occurs in the 5’ to 3’ dir antiparallel to DNA strand
Transient RNA/DNA complexes
Describe transcription elongation
Termination signals tell the polymerase when to stop the DNA template.
One signal is palindromic GC rich followed by AT rich region
New RNA transcript formed in hairpin structure with a stem and loop
Signals for termination are made from what?
Newly synthesized RNA
In prokaryotes when does Transcription and Translation occur?
Together
In Eukaryotes where does RNA synthesis occur?
in the nucleus
In Eukaryotes where does translation occur?
in the cytoplasm
Describe how eukaryote RNA is processed
polyA tail is added to 3’ end to increase stability and specifies export to cytoplasm
Addition of cap to 5’ end
What are three factors that influence gene expression
Nuclear membrane
RNA processing
Complex transcriptional regulation
What does splicing do?
removes introns ( non coding DNA) to allow synthesis of several proteins on one gene
What codes for the splicing sites?
RNA sequence
What performs the splicing?
The spliceosome
How can transcription be controlled?
Interaction of RNA polymerase w/ promoter can be enhanced by activators or blocked by repressor.
In bacteria operon promoter controls this
What is the name for gene that are expressed all the time?
Constitutive expression
What is the name for gene that not expressed all the time?
Regulated expression
Describe the regulation that is associated with Allolactose
Allolactose is an inducer of the operon which binds to the repressor and prevents binding to operator.
SO genes are on when lactose is present
What do these bind to?
Basal Transcription factors
Regulatory Transcriptional factors
Basal- bind to promoters
Regulatory- bind to promotor-proximal elements and enhancers
microRNA or miRNa does what?
regulates gene expression
