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120 Cards in this Set
- Front
- Back
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Genetic Code
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written in linear form, using ribonucleotide bases that compose mRNA molecules as letters
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The sequence of RNA is derived from
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complementary bases in the DNA
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mRNA triple codons specifys
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one amino acid
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the code contains
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start and stop signals to iniciate or terminate translation
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serves as an intermediate in transferring genetic information from DNA to proteins
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mRNA
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The triple code provides ____ to specity the _____
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64 codones, 20 amino acids
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The genetic code reads ___ at a time in a _____, Thus, the code is _____and _____.
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three nucleotides
continous linear manner nonoverlapping commaless |
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Some aminoacids are specifed by more than one codon.
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the genetic code is degenerate
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They are only encoded by a single codon
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tryptophan and methionine
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predicts that hydrogen bonding between the codon and anticodon at the third position is subject to modified base-pairing
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wobble hypothesis
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genetic code shows order
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aminoacids often share one or two middle bases in the triplets endoing them
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Initial amino acid in prokaryotes
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fmet
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do not call for amino acids
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UAG, UAA, and UGA
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To distinguist begging and middle
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fmet and met
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exceptions to the universal genetic code
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some viruses overlapping genes
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serves as intermediate molecule between DNA and proteins during transcription
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RNA
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Directs the synthesis of RNA using DNA template.
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RNA polymerase
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No ______ is required for initiation, and enzyme uses _____ instead of _____________
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primer
ribonucleotides deoxyribonucleotides |
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E.coli contains the subunits___,___,___, and ___
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alpha 2, beta, and beta prime and sigma.
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Transcription begins with _____ by ____ at a _____. The ___ ___ is responsible for promoter recognition.
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template binding
RNA polimerase promoter alpha |
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alpha subunit recognizes ___ in prokaryotes.
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-35
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is for binding in prokaryotes
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-10
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Where does transcription begins
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at the transcription start site. Where DNA is unwound to meke template strand accessible.
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Causes transcription to terminate
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hairpin formation in the RNA or rho termination factor.
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Where does transcription occurs in eukaryotes
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nucleous
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In eukaryotes is transcription coupled?
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no
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In eukaryotic transcription requires ____ remodeling
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chromatin
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kinds of chromatin
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heterochromatin
etchromaitn |
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what influences transcription regulation in eukaryotes
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promoters
enhancers |
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types of promoters
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strong-polimerase will bind to promoter every 1-2 sec
weak-polimerase will bind to promoter ever 20 min |
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requires processing to produce mature mRNAs
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eukaryotic mRNA
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three forms of RNA
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polimerase I,II,III
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Are enhancer required for transcription
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no
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can be upstream or downstream of the gene
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enhancers
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are required to help RNA polymerase II bind to promoter and initiate transcription
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transcription factors
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What are transcription factors?
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...
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is RNA editing only in eukaryotes?
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true
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is a addition of a 5' cap and a poly-A tail
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heterogenous nuclear RNA (hnRNA)postranscriptionally
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what is the cap for
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to bind to small subunit of ribosome
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poly A-tail
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for endonucleases to destroy is a protective mechanism
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In eukaryotes are introns expresed
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no, only exons are expresed
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how are introns removed
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by splicing
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where are exons joined together
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in the mature mRNA
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tRNA live ___ as well as ____. While mRNA lives ____
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long, small
rRNA, small big, 15 min in bac and couple hours in eukaryotes |
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is the biological polymerization of amino acids into polypeptide chain
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translation
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process that requires amonoacids, mRNA, ribosomes, and tRNA
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translation
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serves as adaptor molecules to adapt the triplet codons in mRNA to the correct amino acid
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tRNA
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constist of ribosomal proteins and ribosomal RNAs and have a large subunit and small subunit
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ribosomes
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16s rRNA
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small subunit of prokaryotes
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provide important catalytic functions associated with translation, are moderately and tanemly repetitive
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rRNAs
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are 75-90 nucleotides and have a two dimentional structure like clover leaf
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tRNA
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contain postransciptionally modified bases
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tRNA
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has the anticodon that base-pairs with the codon in the mRNA
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tRNA
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The corresponding amino acid is bound to the CCA sequence at ___ end of all ____
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3'
tRNA |
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tRNA charged is ______ ____ ___. Uncharged is ____ ___ ____ ____.
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carring amino acid
looking for amino acid |
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charges (activates) tRNAs with the apropiate amino acid
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aminoacyl tRNA synthetase
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steps to charge
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1- amaminoacylsinthetase(a) binds to a specific aa
2- aasynthetase binds to a specific tRNA 3- tRNA gets charged |
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specificity is controlled by
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T on left and D on right loops
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three steps of translation
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initiation
elongation termination |
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requires the small and lage ribosomal subunits, charged initiator tRNA, initiation factors and others
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Initiation
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In bacteria the AUG start codon is preceded by_____, which base pairs with a region of the _____ of the _____.
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shine-dalgarno sequence
16 s rRNA 30s small subunit |
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requires ribosomal subunits assembled with the mRNA to form the P site and A site
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elongation
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P and A stand for
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peptidyl
aminoacyl |
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the charged tRNA enters the ____ __, and peptidyl transferase ____ peptide bond formation between the ___ __ on the tRNA at the __ site and the growing peptide chain bound to the tRNA in P site.
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A site
catalyzes amino acid A |
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uncharged tRNA moves to ____ and the tRNA bound to the peptide chain moves to ___
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E site
P site |
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elongation steps
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1-mRNA binds to small subunit
2-tRNA met binds to P site where AUG is 3-large subunit joins 4-now charged tRNA fills A site 5-Peptidyl transferase catalyses peptide bond 6- aa chain on A site moves or translocates to P site 7- A site is availabe to new charged tRNA |
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is signaled by a stop codons UAG
UAA, and UGA |
termination
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release factors cleave the ____ ____ from the tRNA and ___ __ from the translation complex.
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polipeptide chain
release it |
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mRNAs with several ribosomes translating at once
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polysomes
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ribosomes are larger in
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eukaryotes
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in eukaryotes translation is ____ and _____ separated.
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spatially
temporally |
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requires more factors for initiation, translation and termination
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eukaryotes
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Alkaptonuria
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...
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phenylketonuria
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...
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one-gene: one-gene enzyme hypothesis. Nutritional mutations in mold neurospora caused the loss of an ____ ____ that catalyzes essential raction in wild -type organisms.
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enzymatic activity
growth only when aa are provided |
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bcs not all proteins are enzymes and some proteins have more than one subunit hypothesis changed to
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one-gene: one-polypeptide chain
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genetic disease in which one aa change (single point mutation) in the protein affected the shape of the protein
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sickle-cell anemia
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the order of nucleotides in a gene correlates directly with the order of amino acids in the corresponding polypeptide
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colinearity
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order
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1 st structure- nonfunctional
2 nd " -nonfunctional 3 rd " -functional 3D 4th " - functional over one polypeptide chain acting together for one protein |
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crusial modifications for capability of the final protein product
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posttranslationally modification
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structure of alpha helix
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secondary structure
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Beta pleated sheet
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..
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group that confers specific chemical properties
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R group
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peptide bond forms by _____ ____
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dehydration reaction
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what groups are involved in forming peptide bond
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carboxyl group and amino group
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are involved in movement of molecules across membranes
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transport proteins
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example of transport protein
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hemoglobin it transport oxygen
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example of structural proteins
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keratin and collagen
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contractile proteins
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actin and myosin
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function in the immune system of vertebrates
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immunoglobulins
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regulate various types of chemical activity
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hormones and receptors
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bind to DNA in eukaryotic organisms
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histones
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are largest group of proteins involved in catalysis
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enzymes
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fold independently of the rest of protein into stable unique conformations. impart different functional capabilities
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protein domain
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proposed to encode protein domain
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exons
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may be a kind of evolution to form unique gens in eukaryotes
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exon shuffling
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CAP
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catabolite activating protein
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secondary mechanism involved in repressing expression of the lac operon when glucose is present. it operates through an interaction between promoter (lac operon) and the CAP
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CAP catabolite represion
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If glucose is present _____ will not be further metabolized
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lactose
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promoter regions
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CAP site
RNA polymerase site |
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If CAP is not attached transcription will not occur
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false. still occurs but very inefficient. bcs polymerase has a difficult time to recognize and bind to promoter. alpha subunit will not closely bind to -10 for transcription to occur
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CAP binds to ____
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promoter cap site
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CAP +cAMP forms a _____
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cAdenosine MonoPhosphate form a complex
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interferes with the formation of cAMP
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glucose. it makes transcription occur inefficiently. CAP+cAMP cannot attach to DNA
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In prokaryotes structural genes are ______ and specify the amino acid sequence in the polypeptide
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continous
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sequence of DNA that interacts with a specific repressor protein to control transcription of structural genes
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operator
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Induced system. genes are turned on when a specific substrate is present or off when not present
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Lac operon
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negative control
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repressor protein has to be removed from DNA
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Structural genes of lac operon
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lacZ, lacY, and lacA plus a upstream regulatory region with an operator and a promoter
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encodes B-galactose
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lacZ. B-galactosidase converts disaccharide lactose to monosaccharides glucose and galactose
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gene that specifies primary structure of permease
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lacY. permease facilitates entry of lactose into bacterial cell
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codes for the enzyme transacetylase
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lacA. transacetylase is involved in removal of toxic by-products of lactose digestion from cell
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regulatory genes of lac operon
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repressor gene lacI, near structural genes will bind to the other regulatory gene
operator gere-segment of DNA interacts with repressor protein to control trancription of structural genes |
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Represor protein has 2 binding sites
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operator
and lactose |
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if no lactose in medium
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the represor protein rp binds to operator. polymerase cannot get though. transcription cannot occur. lactose is not available to be metabolized
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If lactose present
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lactose to RP transcription proceeds
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mutation of represor gene
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RP will never bind to DNA transcription will not occur
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if a mutation on operator gene
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RP will not bind to DNA transcription will occur constantly
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example of secondary positive control mechanism
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catabolite repression
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how can transcription be turned off
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by the presence of RP
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