Protein Transcription Flashcards
do all cells have the same genomic DNA, and if so, why?
in a single organism, all cells carry the same genomic DNA; it serves as a blueprint for cellular activity
how are there so many different cell types if all cells have the same genomic DNA?
even though all cells have the same blueprint of DNA, it is regulated in how it is expressed/when it is in order to differentiate it
define regulation of gene expression
an efficient way to utilize genes; genes turned on/off as they are needed
in which direction are mrna molecules created?
in the 5’ to 3’, just like in DNA synthesis
define rna polymerase
enzyme that synthesizes rna from a dna template
define the sigma subunit (factor)
positions the rna polymerase at the site of initiation and controls the steps of transcription
why are the -10 and -35 elements important?
these elements act as recognition sites upstream of the start site for the rna polymerase to bind to and initiate transcription
-10 = TATAAT
-35 = TTGACA
transcription start site = +1
define promoter
region of dna where transcription is initiated via the binding of rna polymerase (-10 and -35 is an example)
what is the closed-promoter complex?
initial binding of rna polymerase to a region where DNA is not unwound
what is the open-promoter complex?
it’s formed when the closed complex isomerizes, which opens DNA into transcription bubble; essential for rna polymerase to access DNA template
describe the process of initiation
atleast 5 GTFs needed to begin
1.) a GTF will bind to promoter
2.) recruits another GTF
3.) rna polymerase II will bind WITH an additional GTF
4.) two more GTFs will come in, forming preinitiation complex
this allows initiation IN VITRO; if IN VIVO, there is a need for more factors
describe the process of elongation
rna polymerase will unwind the dna strand in the 3’ direction while also winding it in the 5’
describe the process of termination
phosphorylation on the C-terminal domain will create a binding site for a rna endonuclease
endonuclease will recognize and cleave non-coding sequence after mrna, freeing it
exonuclease will degrade remaining rna sequence and cause rna polymerase II to dislodge
what is a termination signal?
a sequence that signals the end of transcription or translation
what is messenger rna?
type of rna associated with protein-coding genes
what is ribosomal rna?
non-coding rna that forms part of the ribosome
what is transfer rna?
an adaptor rna that assists in decoding mrna; has anticodon that matches to mrna codon
what is rna polymerase II?
complex that transcribes dna into precursors of mrna
describe general transcription factors
dna binding proteins that control the rate of transcription; needed for transcription of all genes
what is the purpose of a promoter element?
it allows for the binding of transcription factors in order to begin initiation
when is a mediator used and why?
complex required by rna polymerase II; used as a coactivator with GTFs and rna polymerase II
describe the c-terminal domain
end of the polypeptide chain with a free carboxyl group; phosphorylation releases active rna polymerase II
describe the difference between an endonuclease and an exonuclease
endo = within; cleaves phosphodiester bonds within nucleotide chain
exo = outside; cleaves phosphodiester bonds at the 3’ or 5’ ends
how many polymerases do prokaryotes have vs how many do eukaryotes have?
prokaryotes = rna polymerase I - V
eukaryotes = rna polymerase I-III
