Lecture 12 Flashcards
Which are the non-tissue-specific types of RNA?
What is the tissue specific type?
rRNA, tRNA, and some “housekeeping” mRNA (i.e. collagen or keratin) comprise the non-tissue-specific.
Tissue specific = mRNA produced and controlled in certain tissues only.
What is the antisense strand vs the sense strand of DNA?
Antisense is the template (complementary) for RNA transcription, whereas the sense strand has identical sequence to the nascent RNA transcript.
What is the smallest type of RNA?
tRNA ( ~ 76 -90 NTs)
What is the most abundant RNA in the body, and about how much of the total RNA in the body does it represent?
rRNA is the most abundant, representing about 80% of all RNA in the body. It is the most important part of Ribosomes!
Which RNA represents about 5% of all endogenous RNA?
mRNA
What are the differences between Eukaryotic and Prokaryotic mRNA?
Prokaryotic is Polycistronic (multiple coding regions), Eukaryotic is Monocistronic.
Prokaryotic RNA does NOT have 5’ cap or 3’ poly A tail
Prokaryotic RNA is transcribed by one, and only one RNA Pol (Eukaryotic RNA is transcribed by a few.)
What is the structure of Prokaryotic RNA Pol, and how do these structures function?
Prokaryotic RNA Pol is comprised of a 5-subunit core enzyme and sigma protein. The sigma protein (the nose of the Pol) is responsible for specificity, recognizing promoter regions of Prokaryotic DNA to begin transcription. #theNoseKnows
What are the sequences recognized by Prokaryotic RNA Pol holoenzyme that facilitate Initiation of transcription?
Pribnow box (TATAAT) located about 7 NTs downstream from start site and a sequence about 35 NTs downstream from the start site.
What is the Prokaryotic RNA Pol termination signal?
Newly formed RNA forms a hairpin that signals termination. The RNA Pol unbinds the DNA and rebinds the Sigma factor.
What does Rifampin do?
It’s an antibiotic that binds Prokaryotic RNA Pol causing a conformational change which prevents initiation of transcription. Key treatment for Tuberculosis.
What is the main point of gene regulation in prokaryotes?
RNA synthesis
What are the key features and modes of regulation for the lac Operon?
In the presence of Glucose, Adenylyl cyclase is not active and does not create cAMP, so cAMP does not bind CAP to aid in initiation. Also, without lactose, the repressor protein made by the lacI gene is free to bind the operator and repress transcription. When lactose is present, it binds in the form of allolactose to the repressor protein and prevents it from binding the operator. It’s the lacY gene that codes for Galatoside Permease, which allows lactose to permeate the cell membrane. Beta galactosidase, coded by the lacZ gene, metabolizes lactose.
What kind of “system” does the lac operon represent?
Inducible system
What are the two mechanisms for induction of the lac operon?
- Allolactose binds the repressor, preventing it from binding the operator.
- cAMP levels rise, helping to facilitate RAN Pol bind the promoter.
What is the shape of the lac operon repressor protein, and how does this help it?
It is a “helix-turn-helix” shape that basically plugs into the groves of double stranded DNA.
