What’s a gene?
Segment of genetic information that codes for a structure or a function
What’s a chromosome?
Organised genetic informatio, including coding and non-coding sequences
What’s a genome?
Entirety of genetic information in a cell, including chromosomal and extra chromosomal information
What are required factors for transcription?
· energy: ribo nucleotides
· matrix: DNA
· machine: RNA Polymerase
What’s important about the transcription in bacteria?
requires sigma factor
Initiated at specific site
Copies one antisense strand
Termination is at specific sites in two different ways
they have operons: genes are transcribed from the same promoter
No nucleus, transcription and translation at once
what are inducers?
small molecules that bind regulatory proteins and change their ability to control gene transcription
what are sigma factors?
transcription factors, which promote broad changes in gene expression0
How can you regulate the Transcription in Bacteria?
promotor strength
alternative sigma-factors
transcription factors
> repressing (negative)
>activating (positive)
>enhancing (increasing expression)
DNA-binding motifs
two-component systems
antitermination and attenuation
mRNA stability/processing
whats important about the replication of prokarzotes and eukarzotes?
Feature
Prokaryotes
Eukaryotes
Compartment
Cytoplasm
Nucleus
Chromosome structure
Usually one circular chromosome
Multiple linear chromosomes
Origins of replication
Single origin per chromosome
Many origins per chromosome
Replication rate
Fast: ~1000–2000 nt/s
Slower: ~50–100 nt/s
Main replicative polymerase
DNA polymerase III (leading & lagging)
Pol ε (leading), Pol δ (lagging), Pol α–primase for primers
Genome organization
Less DNA, no nucleosomes, little non‑coding DNA
Large genome, nucleosomes, much non‑coding DNA
Telomeres / end problem
No telomeres, no end‑replication problem
Linear ends, telomeres + telomerase required
Cell‑cycle timing
Can start any time before division
Restricted to S phase of cell cycle
whats important about the transcription of prokaryotes and eukaryotes?
Cellular location
Cytoplasm (no nucleus)
Coupling to translation
Transcription and translation are coupled (simultaneous)
Spatially separated; transcription in nucleus, translation in cytoplasm
RNA polymerases
One main RNA polymerase for mRNA, rRNA, tRNA
Three main polymerases: Pol I (rRNA), Pol II (mRNA), Pol III (tRNA, 5S rRNA)
Promoter elements
−10 (Pribnow box) and −35 consensus elements
Core promoter (e.g. TATA box) plus many regulatory elements (enhancers, silencers)
Initiation factors
Sigma factor (σ) provides promoter specificity
Many general transcription factors (TFIID, TFIIA/B/E/F/H, etc.)
Primary transcript
mRNA is usually ready for translation immediately
Pre‑mRNA must be processed (capping, splicing, polyadenylation)
RNA processing
Minimal; rare introns
Extensive: 5′ cap, intron removal, 3′ poly(A) tail
what are the polymerases transcribe for?
RNA Pol I → rRNA (28S, 18S, 5.8S).
• RNA Pol II → mRNA, many ncRNAs.
• RNA Pol III → tRNA, 5S rRNA, others.
What are the characteristics of the promotors?
more complex
Less conserved
Variable Elements
Different for each polymerase
Why is capping important?
* Regulation of nuclear export
2. Prevention of degradation by exonuclease
3. Promotion of translation (bound by ribosome)
4. Promotion of 5'proximal intron exision
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