Midterm 2-2 Flashcards
(33 cards)
What does RNA polymerase do
It synthesizes RNA by adding complementary triphosphates nucleotides to the template strand of the DNA sequence. This happens from 5’ to 3’
What does gene expression begin with
Transcription, this begins when an RNA copy of the expressed gene is synthesized by the RNA polymerase enzyme
What is RNA and DnA composed of
RNA: nucleoside triphosphates while DNA is composed of deoxynucleoside triphosphates
What purpose does the promoter serve and what is it
This is the sequence that allows the RNA polymerase bind to the DNA strand. A specific protein binds to it
What is required in transcription
The separation of a DNA sequence that allows the RNA to form a complementary strand on the template
What is the template strand
The strand that is being read
What is the no template strand
The strand that matches the synthesized RNA strand but with t instead of u
How does the RNA polymerase work
It attaches complementary ribonucleotide triphosphates by the hydrogen bonding capacities of the DNA strand
How can the DNA pass through the RNA polymerase
It has various grooves that allow the DNA to pass through the polymerase during catalytic activities
What does transcription initial require
The binding or a sigma protein to the holoenzyme. The sigma will read the DNA and bind to the promoter site (super critical to initiation
How is sigma related to environmental change
It influences what genes are expressed which is why there are multiple forms of sigma. These sigma factors are induced by various environmental conditions such as heat and starvation. Cell will adapt to these situations by switching sigma factors to alter gene expression.
What sequence does the RNA polymerase/sigma complex commonly bind to
-10box and -35 box (done by doing several actities where the sigma bound to and this was the common similarity
Describe the -10 box
This is located 10 bases upstream from the transcription start site 5’-TATAAT-3’
Describe the -35 box
This is located 35 bases upstream from the transcription start site 5’TTGACA-3’
How does the holoenzyme work
Once the sigma finds the correct promoter site it will orient the RNA polymerase core complex for transcription at the gene start site. Then once the polymerase opens up the DNA will be opened up to catalyze the polymerization of nucleotides. It will the. Move down the template as the RNA is synthesized
What is transcription directed by
Essentially the hydrogen bonding between the DNA nucleotides and incoming nucleotides that diffuse into the active site of the polymerase
Is the addition of nucleotides to RNA exergonic or endergonic
Exergonic due to the favor ability of breaking the triphosphate bonds
What happens to the sigma once transcription is initiated
It dissociates from the holoenzyme
How does transcription begin (elongation)
The enzyme elongates the RNA transcript, reading the DNA template and synthesizing 5’-3’ while DNA moves the opposite
When is transcription eliminated
When the transcription termination signal is encountered during synthesis on the DNA template
What are the different ways that RNA can dissociate from the DNA (termination)
When’s the RNA forms a hairpin structure which will pull the RNA molecule out of the holoenzyme
Or another protein can bind to the RNA at the termination sequence which will cause it to disassemble
What are the basic difference between eukaryotes and prokaryote transcription
Eukaryotes have more variability and complexity with much larger RNA polymerase enzymes
Transcription in eukaryotes, how is the RNA polymerase different
They have three RNA polymerases it is mediated by the second one
Transcription in eukaryotes, how is the promoter different
This promoter actually varies in eukaryotes where instead of the sigma, the basal transcription factor binds to the promoter
