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55 Cards in this Set
- Front
- Back
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What does a eukaryoic respressor do? AKA?
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compete with activator for DNA binding site (protein binds directly to DNA)
-inhibits directly through protein-protein interactions -AKA: active respressor |
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What does a corepressor do?
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modify the chromatin structure
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What is chromatin?
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Nucleosome core particle
-146 bp DNA wrapped around histones -1 molecule H1 binds DNA! -2 molecules each of H2A, H2B, H3, H4 |
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What factors can control transcriptional activity of chromatin?
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1. modifications of histones
-methylation -phosphorylation -histone acetylation 2. Nucleosome rearrangement -association of HMGN (non-histone chromosomal proteins) w/nucleosomes 3. Non-coding RNA 4. DNA Methylation |
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What enzyme is responsible for the actylation of the histone tails?
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HAT: histone acetyltransferase
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What are the features that HAT imposes on the histone tails?
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-acetylates histone tails=
1. recruited by 'elongation factors' during transcription 2. associated with actively transcribed DNA 3. increase accessibility of chromatin |
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What is HDAC? What does it do?
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-histone deacetylase, makes DNA wrap tightly around histones to shut off
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What does histone acetylation do? Where does it occur specificity?
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-Reduces net postive charge of histones= weak interaction with DNA & facilitates binding of TFs to DNA
*occurs on core histones H2A, H2B, H3 & H4 1. histone domain (DNA wrapping) 2. amino-terminal domain (extends outside nucleosome) RICH IN LYSINE |
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What amino acids do mehtylation deal with?
phosphorylation? ubiquitination? |
methylation: lysine and arginine
phosphorylation: serine ubiquitination: lysine |
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What is suspected that methylation and phosphorylation do regarding the histone tails?
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provide additional TF binding sites??
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What are two type of non-coding RNA?
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1. RNA interference
-short, dsRNA -includes degradation of homologous mRNA 2. microRNAs (miRNAs) -short, non-coding -regulation gene expression -recruits methyltransferase for H3 lysine-9 |
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What is the RISC? what does it do?
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RISC: RNA induces silening complex
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What is RITS? What does it do?
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RITS: RNA induced transcritpional silecing complex. forms chromatin so transcription is shut off
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What do non-coding RNAs do to the chromatin stucture?
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-induces histone modifications that lead to chromatin condensation to form heterchromatin
Ex: involved in X-chromosome inactivation |
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What does the Xist gene do?
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1. transcribe RNA on inactive chromosome
2. coats chromosome 3. induces methylation of H3, leading to chromosome condensation |
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What is genomic imprinting?
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when one of the egg/sperm cells is methylated=inactive during development of germ cells
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What does mRNA do?
tRNA? rRNA? |
mRNA=carries genetic information
tRNA=decodes message into sequence of AA rRNA=enzyme for protein synthesis |
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List the "Dogma" with enzymes under arrows
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DNA transcription with RNA polymerase to mRNA translation with tRNA to protein
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Which part of the dogma is most regulated?
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transcription
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What is on the 5' and 3' end of mRNA that is extensively modified?
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7-methyl G on 5'
poly A tail on 3' (way to control gene expression) |
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Which end of the mRNA molecule is co-transcriptional? post-transcriptional?
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co-transcriptional=7'
post-transcriptional=3' |
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What is significant about rRNA synthesis?
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all cleaved from one molecule of DNA
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How does rRNA processing (Pol I) take place?
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large precursor transcript is cleaved to form mature rRNA molecules by nucleases
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How does tRNA Processing (Pol III) take place?
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1. 5' cleaved by RNase P (ribozyme=RNA enzyme)
2. 3' cleaved 3. Addition of CCA 4. Base Modification |
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Where does eurkaryotic mRNA processing take place?
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nucleus
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What is the big difference in mRNA processing in eurk. v prok?
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euk=separation of transcription/translation so processing possible
prok=couple transcription/translation, mRNA must be mature |
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Go through the process of mRNA processing to protein
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1. Transcription by RNAP II, during this 7meG cap added
2. cleave at 3' poly A addtion site 3.PAP (poly A polymerase) adds tail 4. spliceosome-snRNA+protein take out introns 5. Transported to cytoplasm 6.nucleases trim poly A tail 7. docks to ribosome for translation |
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Which part of the mRNA is 'junk'?
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introns
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What is required for translation initiation?
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Capping
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What is capping and when does it occur?
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-occurs during transcription
(co-transcriptionally) -7methyl guanosine -linked 5' to 5' |
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WHat is the poly A tail required for?
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-stability
-translation (interacts with 5' cap) |
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What initiates the PAP complex?
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sequences in the RNA chain
-PAP complex associated w/RNA pol II -GU rich sequence (50 bases downstream of poly A addition site) |
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What is mRNA splicing? what is this event directed by?
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cutting on the introns and ligating together the exons
-directed by the primary transcript (pre-mRNA) |
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Describe the splicing mechanism? what is this mechanism carried out by?
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-requires 2 transesterification rxns
-spliceosome carries it out -1.cleavage at 5' splice site to form lariat-like intermediate 2. cleavage at 3' splice site 3. ligation of exons 4. degradation of lariat by cell |
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What is a spliceosome?
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carries out splicing in mRNA-
snRNAs U1: 5' splice junction U2: branch point U4-6: complex U5: stabalization snRNPs are recycled after splicing occurs and mRNA transported |
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What is a ribozyme?
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an RNA molecule with enzymatic activity
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What are the mechanisms of self-splicing?
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Group I: self-splicing introns, use GTP co-factor (no lariat formation)
Group II: no GTP(same as splicosome but no snRNPs) |
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WHat is differential processing referring to?
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-splicing patterns regulate gene proudct identity
-some transcripts spliced differently in different cells -used for tissue specific genen expression -different tissues make different mRNAs from the same primary transcript |
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What does alternative splicing refer to?
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mechanism where exons of use are selected
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What does poly A choice refer to?
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multiple poly A sites
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What does Calcitonin-CGRP do and where are they made? which exons go to each?
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Calcitonin-Ca2+ uptake hormone
-made in thyroid, controls kidney function *CGRP-neuron transmitter -made in pituitary, helps detect taste Calcitonin: 1,2,3,4 CGRP: 1,2,3,5,6 |
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What are two factors that control mRNA stability?
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1. Length of poly A tail: long poly A tail=more stable
2. degraduation sequation: n=o=stable, more AUUUA=less stable |
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What degrades RNA and where can it be found?
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exonuclease, on ribosome
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What gene is involved in the regulation of AUUUA repeat?
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beta-globin gene
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What is the enzyme in the final process of gene expression?
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ribosome for translation
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what decodes the triplet codons?
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tRNA
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What is at the 5' and 3' end of the polypeptide chain?
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5'=amino
3'=carboxy |
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What is the enzyme that catlyses the peptide bond?
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peptidyl transferase
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What is the inition codon?
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AUG
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What is ________?
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degenerate
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Where is the acceptor stem-attachment of AA?
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3' OH
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What determines the accuracy of protein synthesis?
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1)charging of tRNA
2)decoding of the codon on mRNA |
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What does the correct pairing of AA to tRNA?
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amino-acyl tRNA synthetases
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Where does the recognition of tRNA occur?
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identity element bases
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WHat is special about inosine?
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it can substitute as C, U or A
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