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mole. genetics ch.16
prokaryotic transcription
| Question | Answer |
|---|---|
| what is RNA polymerase? | an enzyme that catalyzes transcription, synthesizing mRNA from a DNA strand (template) |
| in what direction does transcription take place? | 5' to 3' on a 3' to 5' template strand |
| what is the promoter? | a special region located upstream of a gene |
| what is involved in the transcription bubble? | RNA polymerase, a coding and template strand, and an RNA strand. the length of the bubble is about 12-14 base pairs long |
| is transcription faster or slower than DNA replication? | transcription is slower than DNA replication |
| what are the stages of transcription? | initiation, elongation, and termination |
| what is the core RNA polymerase? | multi-subunit enzyme that is responsible for catalyzing RNA synthesis |
| what is the sigma factor? | a subunit of the RNA polymerase that has domains which read promoter sequences. it is responsible for promoter recognition |
| what are the conserved regions of the promoter? | essential DNA sequences that remain similar across species to ensure proper transcription initiation by RNA polymerase and binding of transcription factors |
| what are the consensus regions of the promoter | a conserved DNA sequence within a promoter that acts as a binding site for RNA polymerase and transcription factors to initiate transcription |
| what is at the -10 region? | 6-bp region about 10 bp upstream of the start point. the sequence is TATAAT |
| what is at the -35 region? | about 35 bp upstream from the start site and has a sequence of TTGACA |
| why are the -10 and -35 regions important? | they are critical binding sites of the promoter that are recognized by RNA polymerase, initiating transcription |
| does the distance between the -10 and -35 regions matter? | yes because they have specific distances from each other to match the geometry of RNA polymerase |
| what is an up mutation? | mutations that cause an increase of transcription |
| what is a down mutation? | mutations that cause a reduction or loss of transcription of adjacent genes |
| how do bacteria terminate transcription? | occurs at the terminator when RNA polymerase stops adding nucleotides to the growing chain and releases the product, dissociating from template. may require both recognition of terminator sequence in DNA and formation of a hairpin structure in RNA product |
| what is an intrinsic terminator? | terminators that do not require additional protein factors to end transcription. they consist of a G-C rich hairpin followed by a U-rich region in which termination occurs |
| what is a rho-dependent terminator? | terminator that requires additional proteins to end transcription, such as a protein called a rho factor |
| what is a rut site? | the sequence of RNA that is recognized by the rho termination factor |
| how does rho work? | it binds to the rut site on RNA and tracks along the RNA to release it from the RNA-DNA hybrid structure at the RNA polymerase |
| is bacteria mRNA unstable? | yes it is, and is the reason mRNA is translated into polypeptides for a few minutes |
| can transcription and translation occur at the same time? | yes they can, but only in bacteria/prokaryptes. both processes are transcribed |
Created by:
angievelasco