Chapter 8 Flashcards
Transcription
Copying of DNA into RNA
Cell accesses it’s data in genome via…
Transcription
RNA is based off _______ DNA strand
Complementary strand
Define holoenzyme
Holo means all inclusive
Consists of core polymerase and sigma factor required for initiation
What process needs polymerase?
Required for elongation
What process requires sigma factors?
Initiation
What do sigma factors and RNA polymerase do?
They bind and guide RNA to specific DNA sequences called promoters
What do you call a sigma factor that is made in large quantities and used all the time?
Housekeeping sigma factor
Consensus sequence
DNA sequence similarities among different promoters recognized by the sigma factor
Consists lf most likely base of each position of predicted promoter
Three stages of transcription
Initiation, elongation, termination
Describe initiation ( transcription)
Sigma factor of holoenzyme binds promoter to dna
Promoter unwinds one helical turn
RNA polymerase binds
Open complex form of RNA polymerase begins transcription
Describe elongation ( transcription)
RNA chin is extended by sequential addition of ribonucleotides from nucleoside triphosphate
Sigma dissociates after 9 bases
Original RNA polymerase continues along template
Unwinding makes 17 bp bubble
Positive supercoils upstream are removed by DNA topoisomerase
Describe termination (transcription)
RNA pol detached from DNA
Rho dependent termination
Relies on rho protein and a strong pause site at 3’ end
Rho independent
Requires GC rich region that causes RNA stem and loop to form and causes RNA pol to pause