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What is the central dogma and what are the exceptions to it?
- DNA -> RNA -> protein
- Exceptions can occur from reverse transcriptase
Describe the process of transcription (including initiation, elongation, and termination)
- RNA polymerase recognizes and binds to the promotor
- DNA converted from ds to open structure
- RNA polymease initiates RNA synthesis, no primer req
- Chain elgonation occurs uder a core enzyme until it reaches a termination sequence [often forms a hairpin loop]
- RNA molecule released
What are the similarities and differences that exists between transcription in pro and euk re: promotor region and termination
- pro promotor: located 5' region upstream from point of initial transcription. Once RNA polymerase binds there the helix is denatured.
- TATAAT: located 10 nucleotides upstream [pribnow box]
- TTGACA: located 35 nucleotides upstream
- euk promotor:
- TATA box: located 35 nucleotides upstream [Hogness box]
- CAAT box: located 80 boxes upstream
What are the modifications are are required in pre-mRNA produced in eukaryotic cells before they can be shipped into the cytoplasm?
- 5' cap: protects 5' end of molecule from nuclease attack, important to subsequent processing
- 3' poly-A tail: protects RNA from degredation, critical for transport to cytoplasm
- Removal of introns: via ssRNA or spliceosomes
What are the different mechanisms available for splicing?
- ssRNA: ribozymes. intron is removed, and RNA ligase joins the two remaining strands.
- Spliceosome: huge molecular complex. snRNA + proteins = snRNP. snRNP forces intron into lariat and removes. Exons are ligated and snRNPs released.
What are the 4 major types of RNA that exist and what is the role of each?
- mRNA: carries message between DNA and ribosome
- rRNA: structural RNA for ribosome
- tRNA: retrieves amino acids based on mRNA sequence
- ribozymes: ribosomes with catalytic abilities (cleavage, ligation)
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