RNA Synthesis & control in Bacteria Flashcards
Copying DNA base sequence by replicating into RNA format
Transcription - pre-mRNA
General nature of Transcription
DNA to RNA TO Protein
Does transcription of the whole genome occur during RNA synthesis?
No, only a section of dsDNA is transcripted to form a ssRNA.
What controls which genes are transcribed where and when?
Regulatory elements such as terminal and start sequence of bases found in the DNA generally control this element.
Region of DNA that leads to initiation of particular gene
Promoter region
Strand of DNA that holds the information.
Non-template strand or coding strand.
Which strand is copied to receive the same information as the coding strand?
The template strand. By producing RNA from this strand allows complementary base pairing to form the same information as the coding strand which is required to form polymers of RNA.
Uracil is only found in RNA
Yes, RNA uses Uracil in place of Thymine in RNA strands.
Which way does RNA transcription occur?
An RNA strand is synthesized in the 5’ to 3’ direction. The template strand is followed in the 3’ to 5’ direction.
In prokaryotes transcription is catalysed by…
a single RNA polymerase. It can also unwind DNA.
Three main types of RNA found in bacteria and eukaryotes?
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)
Along with the three main types of RNA found, which additional type of RNA found in which species?
snRNA - small nuclear RNA
microRNA and siRNA.
Found in eukaryotes only.
What are the RNA molecules that are known to help regulate the translation of RNA?
microRNA and siRNA (Short interfering)
Role in RNA processing?
snRNA. This is found only in eukaryotes along with the regulatory molecules.
3 important regions in bacterial structural genes
- Promoter region
- Coding region
- Termination sequence
When the promoter region and termination sequences are translated, what does this result in the pre-mRNA?
Leadeer/trailer sequence which are untranslated.
Spliced from the strand to become mRNA
What is the significance of the -35 sequence and -10 sequence found in E. coli DNA?
Critical for specifying the initiation of transcription.
Where are the -35 and -10 sequences found?
Before the start of transcription (no. of bp away)
Enzyme that binds to promoter region to begin transcription
RNA polymerase holoenzyme
Holoenzyme is made up of 4 subunits. What are they?
Two a, b and b’
Sigma factor - essential for recogintion of promoter sequence.
Binding of RNA polymerase leads to…
- RNA polymerase loosely binds to -35 sequence
- Tighter binding around -10 sequence leads to untwisting of DNA into ssDNA
- High A/T content helps with forkming ssDNA
Recognition of termination comes from…
RNA polymerase recognising signals for chain termination.
Leads to:
- Release of RNA chain
- Release of enzyme from the template strand.
Why do RNA strand that are being synthesized form hairpin loops?
Regions of complementary sequence within the RNA molecule produce antiparallel double stranded RNA regions separated by unpaired segments of RNA – forms “loops”
Hairpin loop forms which marks termination of transcription.
