module 7 lec 3 Flashcards
What are the two strands of DNA in information flow.
The two strands of DNA are the RNA-like strand and the template strand.
What are the two components of the RNA polymerase in prokaryotes?
The core enzyme and the sigma factor.
What is the role of the sigma factor in prokaryotic transcription?
The sigma factor helps RNA polymerase recognize and bind to the promoter sequence, determining the important sequences for initiatio
What is the equivalent of RNA polymerase in eukaryotes?
Eukaryotes have RNA polymerase (several types depending on the class of genes being transcribed).
How does DNA separate during transcription initiation?
The DNA strand separates temporarily into a RNA-like strand and a template strand.
Which DNA strand is used to synthesize mRNA?
The template strand is used to synthesize messenger RNA, which is complementary to it
In which direction is mRNA synthesized?
mRNA is synthesized in the 5’ to 3’ direction.
Where is the termination region found?
The termination region is encoded in the DNA
What happens during transcription elongation?
During transcription elongation, the transcription bubble moves down the DNA, continuing the process of RNA synthesis.
What is the transcription bubble?
The transcription bubble is a region where the DNA is locally unwound so that RNA polymerase can access the template strand.
How does the transcription bubble move?
The transcription bubble moves along the DNA, as RNA polymerase adds complementary nucleotides to the growing mRNA strand.
What direction is RNA synthesized during elongation?
RNA is synthesized in the 5’ to 3’ direction during transcription elongation.
How is the mRNA strand formed during elongation?
The mRNA strand is formed by RNA polymerase adding complementary RNA nucleotides to the template strand of DNA.
What happens to the DNA ahead of the transcription bubble?
Ahead of the transcription bubble, the DNA re-winds back into its double-stranded form.
How does RNA polymerase advance along the DNA during elongation?
RNA polymerase advances by unwinding the DNA in front of it, adding nucleotides to the mRNA, and rewinding the DNA behind it.
What is the role of the template strand in transcription elongation?
The template strand of DNA provides the sequence for RNA polymerase to synthesize the complementary mRNA strand.
What signals RNA polymerase to release during transcription termination?
A hairpin loop formed in the mRNA signals RNA polymerase to release and stop transcription
What is a hairpin loop in the context of transcription termination?
A hairpin loop is a secondary structure in the mRNA formed by complementary base pairing that causes RNA polymerase to dissociate from the DNA.
How does the hairpin loop affect RNA polymerase?
causes RNA polymerase to release the mRNA and stop transcription.
Where is the hairpin loop formed during transcription termination?
The hairpin loop is formed in the mRNA sequence as it is being transcribed, typically at the terminator sequence.
What happens to the mRNA after RNA polymerase is released during termination?
The mRNA is released from the DNA, completing transcription.
What marks the end of the transcription process in prokaryotes?
In prokaryotes, transcription termination is often marked by the formation of a hairpin loop in the mRNA, followed by the dissociation of RNA polymerase.
Is transcription termination the same in all organisms?
No, transcription termination mechanisms vary between prokaryotes (e.g., hairpin loop) and eukaryotes, where additional factors are involved.
What is the role of the template strand in transcription?
The template strand serves as the pattern for synthesizing mRNA during transcription.
What is the role of the RNA-like strand?
The RNA-like strand is complementary to the template strand and has the same sequence as the mRNA (except for thymine being replaced by uracil).
How does mRNA relate to the information flow in the central dogma?
mRNA serves as the messenger carrying genetic information from DNA to the ribosome for translation into a polypeptide.
What is the final outcome of information flow from DNA to protein?
The information in DNA is transcribed into mRNA, which is then translated into a polypeptide (protein).
How is mRNA related to the polypeptide?
mRNA provides the sequence of codons that directs the synthesis of a polypeptide during translation.
What happens during translation?
During translation, the mRNA sequence is used to assemble amino acids into a polypeptide chain.
What is a promoter in transcription?
A promoter is a DNA sequence that signals where transcription should begin.
What key sequences are found in bacterial promoters?
Bacterial promoters typically have -10 (Pribnow box) and -35 sequences that help RNA polymerase bind and initiate transcription.
What is the TATA box in eukaryotic promoters?
The TATA box is a conserved DNA sequence (~TATAAA) found in eukaryotic promoters, typically around 25-30 bases upstream of the transcription start site.
How do bacterial promoters guide transcription initiation?
In bacteria, the sigma factor binds to the -10 and -35 regions of the promoter, allowing RNA polymerase to initiate transcription.
What role does the TATA box play in eukaryotic transcription initiation?
The TATA box helps recruit transcription factors and RNA polymerase II to the promoter, initiating transcription in eukaryotes.
How do promoters determine where transcription starts in both prokaryotes and eukaryotes?
Promoters contain specific sequences (-10 and -35 in bacteria, TATA box in eukaryotes) that direct RNA polymerase and associated factors to the transcription start site
what does sigma factor do
responsible for determining what are important sequences in promoter.
sigma factor is
prokaryotic
