If protein cant recognize anything that it is supposed to bind it will bind to

If protein cant recognize anything that it is

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If protein can’t recognize anything that it is supposed to bind, it will bind to rho factor, make it bigger and stall ribosome
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o If it finds what it’s looking for, rho factor remains the same and ribosome can transcribe TRANSCRIPTION IN EUKARYOTES 7-methyl guanosine caps added to 5’ end o binds proteins and protects 5’ from degradation poly(A) tails added to 3’ ends o poly(A) polymerase adds poly(A) tails, after cleavage, which are tracts of adenosine monophosphate o enhance stability and play role in transport from nucleus to cytoplasm if introns present, they are removed by RNA splicing o snRNP complexes called “spliceosomes” remove introns and splice exons together RNA polymerase o All eukaryotic RNA polymerases require assistance of other proteins called transcription factors in order to initiate synthesis of RNA chains o I: catalyzes the synthesis of all ribosomal RNAs except small 5S RNA o II: transcribes nuclear genes that encode proteins and perhaps other genes specifying hnRNAs o III : catazlyzes the synthesis of the transfer RNA molecules, the 5S rRNA molecules, and small nuclear RNAs o IV : small interfering RNAs o V : some siRNAs plus noncoding (antisense) transcripts of siRNA target genes Initiation Initiation of transcription by RNA polymerase II requires assistance of several transcription factors Promoters recognized by RNA polymerase II o CAAT BOX : GGCCAATCT -80 o TATA BOX : TATAAAA 5’ 3’ and at -30 o first A 4bp after TATA: +1 position : transcription start site o present in RNA polymerase ii PROMOTERS GC BOX: GGGCGG OCTAMER BOX: ATTTGCAT Elongation Once RNA polymerases released from initiation complexes, they catalyze RNA chain elongation same way as in prokaryotes 5’ ends of mRNA modified by 7-methyl guanosine caps Termination 3’ ends produced by endonucleolytic cleavage rather than termination of transcription
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o cleavage event occurs 11-30 nucleotides downstream from an AAUAAA sequence and upstream from a GU-rich sequence near end of transcript o after cleavage, poly(A) polymerase adds poly(A) tails to 3’ ends polyadenylation Introns: not required for normal gene expression so many eukaryotic genes don’t have introns are spliced out by spliceosomes o composed of snRNPs (snRNA protein complexes) and proteins o Five snRNAs: U1, U2, U4, U5, U6 Introns are removed, and 2 exons on either side are joined together o 3’ end of exon 1 joins 5’ end of exon 2 how to tell if there is intron: if at 5’ end there is a GU and at 3’ end there is an AG, and the intron bonding site UACUAAC (TAC BOX) is present o everything between GU and AG is the intron and gets taken out
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PROTEIN SYNTHESIS Ribosomes form peptide bonds o distributed through cells in prokaryotes, located in cytoplasm in eukaryotes o composed of one large and one small subunits which dissociate when the translation of an mRNA molecule is completed o E.coli: Small 30S subunit and large 50S subunit o Mammalian ribosome: Small 18s subunit and large subunit contains 5S, 5.8S, 28S o
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  • Fall '13
  • DNA, RNA molecules, rna polymerase

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