5c slides Flashcards
what are general trasncription factors essential for
the transcription of all protein encoding genes and initate transscription
specific transcription factors regaulte gene expression of
specific genes by binding to specific regions of those genes that they are controlling
example of specific trascription factor
activator and repressors
role of transcription factor
1.. activator proteins bind to distal control eleemts
2. dna bending protein brings bound activators closer to promoter
3. activators bind to certain mediator proetins and general ytanscription gactors forming an active transcripion initation complex on promoter
what is there was a mutation in the distal control element that affacted the binding of the activators
iy could prevent initatino of transcription
what will partiular combination of control elements activiate
trancription only when the appropriate activator proteins are present
how does specific transcription allow
for tissue spefici gene expression
co expressed euaryotic genes are not organized in
operson
where are co expressed genes typically scattered over
different chromosomes but each has the same combination of contorl elements
activator proetins the the nucleus recognize specific control elements and promote
simulateneous transcription of the genes
what does an external cellular signal itiate
gene expression of coepxressed genes
how doe sthe operon organization of related genes implsofy the regaltion of gene expression in bacteria compred to eukaryotes
in summar gene expression in bacteria via the operon system is more simple and efficient and does not require coordination across different segments of DNA and as many moving parts (transcription factors, cell signals) as eukaryotes. This allows bacteria to rapidly respond to changing environmental conditions which is advantageous.
Similarities and differences in gene expression between Prokaryotes and Eukaryotes
Prokaryotes:
-Operons
-mRNA ready to be translated by ribosomes
-Promoter
Eukaryotes
-No operons
-Pre-mRNA -> mRNA (introns removed, exons spliced together, cap and tail added on either end)
-mRNA exported from nucleus
Initiation of gene expression is more complex
-Promoter
what percent of multicellular euaryotes actually encodes proteins
1.5%
how much of a human genome is transcribed at some point
75%
