Transcription (Bacteria) Flashcards
What is transcription?
Process by which information in a strand of DNA is copied into messenger RNA (mRNA)
How is RNA synthesized?
Catalyzed by RNA polymerase
What is sense DNA strand?
Same side of mRNA
What are promoters?
DNA sequences that lie “upstream” of gene
What are promoter sequences?
Sequences are recognised by RNA polymerase and tells RNA pol. where to start transcribing DNA into RNA
True or false: Is the sequence of the sense DNA strand is sequence of the mRNA transcript?
True. mRNA synthesizes the top strand/coding strand/sense strand and replaces T with U
What are the three stages of DNA-directed RNA synthesis transcription?
- Initiation
- Elongation
- Termination
Describe the initiation process
RNA pol. recognizes and binds to promoter sequence on DNA
RNA pol. unwinds DNA template
What does RNA polymerase do on promoter?
Sits on promoter and melts the strands “off” each other
Describe the elongation process
RNA pol. elongates new RNA molecule
Nucleotides are added
Substrates, ribonucleoside triphosphates are hydrolyzed
Describe the termination process
Special DNA sequences terminate transcription
RNA pol. is released from DNA and free to initiate transcription again
What is the coding sequence?
Region of transcript that is translated
What is RNA polymerase?
Large multi-protein complexes
Homodimer and heterodimer subunits
What does transcription require?
Requires specific sequences in template DNA to direct and modify RNA polymerase activity
What do regulatory proteins do?
Bind within region of transcription start point and act to increase or decrease polymerase activity
What recognizes promoter sequence?
RNA pol. cannot bind to promoter sequence
Sigma factors bind to two sequences
Give an overview of transcription in prokaryotes
Core enzyme forms complex with sigma factors
Enzyme forms a complex with promoter
DNA is unwound
RNA synthesis begins by adding rNTPs
Sigma factors dissociates
RNA synthesis continues
What is the common transcription terminator?
Hairpin loop which is formed by complementary sequence with RNA
How does hairpin loop interfere with transcription?
Destabilized process by interfering with enzyme active site
What are operons?
Clusters of co-regulated genes involved in same process and transcribed onto single polycistronic mRNA
