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33 Cards in this Set
- Front
- Back
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central dogma of molecular biology
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detailed residue-by -residue transfer of sequential information from DNA to RNA to Protein
CANNOT go from protein to nucleic acid |
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DNA replication
Transcription Translation |
DNA to DNA
DNA to RNA RNA to Protein |
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Reverse transcription
viral replication pirons |
RNA to DNA- in retroviruses and telomere replication
RNA to RNA in RNA viruses Mis-folded proteins that can alter conformation of other proteins on contact- spongiform encephalopathy |
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Properties of RNA
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single stranded
Ribonucleotides- ribose sugar with 2' and 3' OH groups Nitrogenous bases- Uracil replaces Thymine Ribozyme- RNA with catalytic activity |
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Messenger RNA
Functional RNA |
encode amino acid sequences to polypeptides
function as RNA molecule (ex) ribosomal RNA (rRNA)- catalyze peptide bond formation in ribosomes Transfer RNA (tRNA)- bring amino acids to mRNA and ribosomes during translation Small Nuclear RNA (snRNA)- splicing introns in spliceosomes |
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Transcription
template non template |
synthesis of RNA from DNA template
(non-coding/anti-sense) 3' to 5' strand read during transcription to produce anti parallel and complementary RNA molecule 5' to 3' strand, same sequence as transcribed RNA molecule |
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Upstream
Downstream |
nucleotides located 3' of transcription start site for RNA coding sequence on template strand 5' on non-template stand
nucleotides located 5' of transcription start site on template strand and 3' on non template strand |
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4 stages of bacterial transcription
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promoter recognition
chain initiation chain elongation chain termination |
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Promoter
consensus sequence 10 box 35 box |
specifies site of transcription initiation. Where RNA polymerase binds to DNA. upstream of transcription start site. not transcribed
sequence typical of bacterial promoters upstream of start site (+1) typical promoter sequences located # of boxes away from start site |
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sigma factor
RNA polymerase holoenzyme |
recognizes and binds to the promoter- released once transcription initiated
5 subunits of RNA polymerase + factor |
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3 steps to initiation
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1. DNA polymerase holoenzyme binds to ds consensus sequence
2. RNA phe unwinds short region (~18 nucleotides of DNA) 3. RNA phe polymerizes 8-10 nucleotides and releases sigma factor DNA reanneals after RN.A polymerase passes |
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Chain Elongation
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1 RNA polymerase adds new nucleotides in 5' to 3' direction in RNA coding region on gene
RNA is anti parallel and complementary to DNA template strand DNA reported as coding strand read 5'-3' RNA transcripts reported 5'-3' RNA synthesized 5'-3' DNA template read 3'-5' ribonucleotide triphosphates added to growing strand in 5'-3' by RNA polymerase |
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polycistronic RNAs
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contain amino acid coding regions for more that one gene
translation coupled with transcription |
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Chain termination (3 steps)
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1. RNA transcript detaches from RNA polymerase
2. RNA polymerase detaches from DNA strand 3. DNA re-anneals as double helix |
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RNA transcript
5' untranslated Region 3' untranslated region |
transcribed region between transcription start site and translation start site does not include promoter sequence
transcribed region between translation stop site and transcription stop site including terminator sequence |
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Eukaryotic Transcription
RNA polymerase II |
more complex, more genes and non-coding DNA= more complex gene regulation with diverse promoters and consensus sequences
3 RNA polymerases transcribes protein coding genes (mRNA, snRNA and others in nucleus) |
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chromatin
primary transcript (pre mRNA) |
DNA associated with proteins with more complicated regulation of expression
genes located in nucleus that must be processed and moved to cytoplasm before being translated |
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cis-acting elements
trans-acting elements |
regulatory DNA sequences involved in eukaryotic transcription initiation to regulate genes located on the SAME chromosome
regulatory proteins involved in Eukaryotic transcription initiation to regulate genes located on different chromosomes |
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eukaryotic promoters
core promoter (TATA box) Promoter-proximal elements |
diverse consensus sequence that vary among different genes
6bp consensus sequence located -25 position upstream +1 cic-regulatory sequence located upstream TATA box that influences efficiency of promoter |
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trans-acting factors
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proteins that recognize different consensus sequences
important in regulating transcription of different cell types |
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general transcription factors (GTFs)
Basal transcription apparatus |
proteins that bind with TATA box in eukaryotes
consists of general transcription factors and RNA pol II bound to TATA box upstream of +1 and produces basal levels of transcription |
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pre-initiation complex
enhancers activatiors |
consists of all GTFs and RNA pol II bound to TATA box + activators and enhancers
cis-regulatory sequences that when bound to activators increase transcription rates trans-acting regulatory proteins that bind to ppe and enhancers to increase efficiency of initiation |
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silencers
repressors |
cis-regulatory sequences that when bound by repressors inhibit transcription
trans-acting regulatory proteins that bind to ppe and silencers decreasing efficiency of initiation |
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signal transduction pathways
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series of events that release and activate trans-action factors bound to transmembrane proteins in response to chemical or physical signals
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elongation in eukaryotes
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like in prokaryotes
rNTPs are added to growing strand at 3' OH by RNA polymerase |
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bacterial vs eukaryotic
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bac- transcription and translation coupled
euk- transcription in nucleus and translation in cytoplasm = more stable RNA transcripts |
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capping
intron splicing polyadenylation |
addition of 5' cap after transcription initiation
removal of introns during elongation addition of 3' polyA tail during temination |
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5' methylguanosine (MeG) cap
5'-5' triphosphate linkage |
guanine attached to 5' end of growing RNA strand with methly group attached = 7-methlyguanosine
nucleotides attached by 5' phosphate groups protects RNA from degredation by exonuclease- removal of nucleotides from ends of RNA molecules |
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introns
extrons |
intervening sequences in non-amino acid coding regions of RNA transcript
expressed sequences in amino-acid coding regions of RNA transcript |
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spliceosome
small ribonucleoprotein particles self splicing introns |
ribonucleoprotein complex composed of..
complexed with other proteins involved in removal of introns ribozymes, RNAs that catalyze splicing of their own introns |
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3' polyA tail
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following termination, 20-200 Adenines added to 3' end function to facilitate transport of mature mRNA across nuclear membrane, protect mRNA from regredation, enhances translation by enabling ribosomal recognition
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alternative pre mRNA processing
alternative splicing alternative promoters alternative polydenylation |
3 mechanisms that allow a single gene to produce multiple polypeptides
pre mRNA in different cells initiate transcription at different +1 uses different termination signals to produce different mature mRNAs |
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alternative splicing
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utilization of different splice sites associated with introns can allow one gene to have many different gene products
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