3 - Gene organisation and transcription I Flashcards
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What is gene expression?
DNA to RNA to Protein.
Occurs in cell nucleus. RNA is exported to cytoplasm.
How many types of RNA polymerases do eukaryotic cells have?
3
What does RNA polymerase I do?
Transcribes rRNA genes.
What does RNA polymerase II do?
Transcribes genes encoding proteins in mRNA.
What does RNA polymerase III do?
Transcribes tRNA and 5S RNA genes.
What is transcription?
Making an RNA copy of a DNA strand.
How does transcription happen?
Ribonucleotide bases are joined by phosphodiester bonds, in 5’ to 3’ direction.
Which strand is used as the template for transcription?
AnTisense
Which strand is identical to the mRNA?
Sense
What does the basal transcription complex do?
Allows RNA polymerase II to be phosphorylated and then engage in transcription.
How is the level of transcription regulated?
By DNA binding proteins called Transcription Factors.
In the absence of binding of other Transcription Factors this produces a Basal (low) level of transcription.
How do transcription factors work?
Transcription factors “bend DNA” on binding. They can interact with each other and the Basal Transcription Complex to modulate transcription.
What does TATA do?
Specifies the initiation point for transcription by RNA Pol II.
What binds to TATA?
TF IID.
What does TF IID do?
Contains TATA binding protein (TBP) and TBP Accessory Factors (TAF’s).
It partially unwinds the DNA helix, widening the minor grove.
