Focus Question:Focus Question:
How does transcription How does transcription work in prokaryotes and work in prokaryotes and eukaryotes?eukaryotes?
IB Topic 7.3 TranscriptionIB Topic 7.3 Transcription
The “Players”The “Players”
DNADNA RNA polymeraseRNA polymerase mRNAmRNA RibosomeRibosome tRNAtRNA Amino acidsAmino acids
DefinitionDefinition
Transcription-Transcription- the the reading and reading and recording of DNA recording of DNA code. code.
Location: NucleusLocation: Nucleus
Direction of TranscriptionDirection of Transcription
Occurs in the 5’Occurs in the 5’3’ 3’ direction (with direction (with reference to the reference to the mRNA)mRNA)
IB Terms: IB Terms: Sense vs. Antisense strandsSense vs. Antisense strands
Sense strand-Sense strand- the the “other” strand, not “other” strand, not transcribed.transcribed.
Antisense strand-Antisense strand- the the one mRNA attaches to, one mRNA attaches to, and is complimentary and is complimentary to.to.
mRNA is similar to the mRNA is similar to the sense strand, except sense strand, except TTU.U.
New…the “Middle” StepNew…the “Middle” Step
Transcription- beginningTranscription- beginning Middle = mRNA processingMiddle = mRNA processing Translation- endTranslation- end
RNA processingRNA processing Post-transcriptionalPost-transcriptional
Introns-Introns- non-coding non-coding sequences are sequences are removedremoved
Exons-Exons- coding coding sequences are spliced sequences are spliced togethertogether
New Players: Prokaryotic New Players: Prokaryotic TranscriptionTranscription
Promoter-Promoter- place on gene where RNA place on gene where RNA polymerase initially attaches.polymerase initially attaches.
Terminator-Terminator- place on gene where place on gene where transcription ends.transcription ends.
RNA Nucleotides = Ribonucleoside RNA Nucleotides = Ribonucleoside TriphosphatesTriphosphates
Similar to Similar to deoxynucleoside deoxynucleoside triphosphates. triphosphates. Serve as the Serve as the building blocks for building blocks for mRNA.mRNA.
Can work from 5’ to Can work from 5’ to 3’ OR 3’ to 5’3’ OR 3’ to 5’