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what subunit is responsible for promoter recognition?
sigma unit of RNA polymerase
what are the two consensus sequences in RNA polymerase and what are their placements?s
TTGACA and TATAAT positioned at -35 and -10 with respect to transcription initiation site
when does sigma component of RNA polymerase dissociate from the holoenzyme?
after 8-9 nucleotides have been transcribed
how do we know that genetic code was nonoverlapping?
- point mutations only caused changes in one amino acid
- more 16 combinations of three amino acids were possible were possible in the nonoverlapping sequence
encode multiple nonoverlapping proteins in mRNA
what are the different types of RNA and what are their functions?
- mRNA *coding
- structural *rRNA
- regulatory functions *miRNA
- catalytic (ribozyme if within ribosome)
what are segments of DNA that can be transcribed to RNA
what is the role of RNA I
rRNA in nucleolus
what is the role of RNA pol II, and III
- mRNA, snRNA for Pol II in the nucleoplasm
- III= 5S RNA, and tRNA
what is the TATA box
- a core promoter element about 35 bp upstream of transcription start site that binds the TATA binding protein of transcription factor TFIID and determines the start of transcription
- CAAT protein is 80bp upstream
what is the role of enhancers
it can modulate transcription from a distance, it may be upstream, down or within a gene
what is the role of general transcription factors?
they help RNA POL II bind to promoter and initiate transcription
what precedes the ORF
what are post-transcriptional modifications made to mRNAs?
5' 7 methyl-gcap and polyA tail
what are spliceosomes
introns are spliced out of the primary transcipt (pre-mRNA)
what is the insertion/deletion of RNA editing
having uridines added to an individual transcript, usually forming the initial codon and then bringing the rest of the sequence into proper reading frames
in trypanosomes it is directed by gRNA (guide RNA) templates. They base-pair with pre-edited mRNAs to direct the editing machinery to make the correct changes.
what is substitution editing and what is a good example of this?
where the identities of individual nucleotides are altered, changing the amino acid coding. apoliproteinB, changes codon to a stop codon
what is the meaning of degenerate?
more than one codon for some amino acids
proteins are encoded by