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53 Cards in this Set
- Front
- Back
Define attenuation
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The regulation of transcription termination as a mechanism of control of gene expression of some bacteria
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Define attenuator
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The terminator sequence at which attenuation occurs
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Define autoregulation
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The control of the transcription of a gene by its own gene product
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Define CAP (catabolite activator protein), or CRP (cAMP receptor protein)
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A positive regulator protein activated by cyclic AMP and needed to initiate transcription of certain operons susceptible to catabolite repression in E. coli
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Define constitutive gene expression
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The continued expression of a gene that does not respond to regulation
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Define coordinate regulation
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A common control of a group of genes
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Define corepressor
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A small molecule which triggers the repression of transcription by binding to a repressor protein
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Define derepressed
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Synonymous with induced when describing the expression of a normal gene which is turned on, and with constitutive in describing the effect of a mutation
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Define diauxic growth
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Biophasic growth on a mixture of two carbon sources in which one carbon source is used up before the other one is mobilized
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Define endproduct feedback inhibition
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Inhibition of the activity of any enzyme which catalyzes an early step in the pathway by a product of the metabolic pathway
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Define hairpin
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A double-helical region formed by base pairing between adjacent (inverted) complementary sequences in a single strand of RNA or DNA
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Define inducer
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A small molecule that triggers gene transcription by binding to a regulatory protein
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Define induction
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Switching on transcription of genes when the substrate of the induced enzymes are present as a result of interaction of the inducer with the regulatory protein
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Define merodiploid
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An organism that is diploid for some but not all of its genes
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Define negative regulation
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Regulation mediated by factors that block or turn off transcription
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Define operator
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The site on DNA at which a repressor protein binds to prevent transcription from initiating at the adjacent promoter
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Define operon
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A unit of bacterial gene expression and regulation, including structural genes and control elements in DNA recognized by regulator gene products
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Define pleiotropic
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Affecting more than one (apparently unrelated) phenotypes
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Define polycistronic mRNA
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It includes coding regions representing more than one gene
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Define positive regulation
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Regulation mediated by a protein that is required for the activation of a transcription unit
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Define promoter
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A region of DNA involved in binding of DNA-dependent RNA polymerase to initiate transcription
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Define regulatory genes
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Encoded gene products that control the expression of other genes
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Define repression
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Inhibition of transcription (or rarely translation) by binding of repressor protein to specific site on DNA or RNA
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Define repressor protein
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Binds to operator on DNA to prevent transcription initiation
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Define signal transduction
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A system that passes a signal received by a receptor through a series of intermediate molecules until final regulatory molecules, such as transcription regulators, are modified in response to the signal
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Define SOS response
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The coordinate induction of many enzymes in E. coli, including repair activities, in response to irradiation or other damage to DNA; results from activation of protease activity by RecA to cleave LexA repressor
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Define terminator
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DNA sequence which causes RNA polymerase to terminate transcription
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Define uninducible
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Mutants that cannot be expressed at all
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What does enzyme induction or repression refer to
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The regulation of enzyme synthesis rather than enzyme activity
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Where is regulation of enzyme synthesis by repression or induction at
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The level of transcription initiation
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What induces the synthesis of degradative (catabolic) enzymes
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Substrate or substrate analog
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What represses the synthesis of biosyntheic (anabolic) enzymes
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The end product
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What are the components of the DNA-dependent RNA polymerase holoenzyme
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The core enzyme (alpha,alpha, Beta, Beta') and the sigma factor which governs the recognition of promoters by the holoenzyme
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What is the rho factor required for
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Transcription to terminate at certain (rho dependent) termination sites
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What genes are constitutively expressed
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Many genes encoding so called "house-keeping" functions. Transcription initiation of these genes is not regulated by accessory proteins
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How are genes negatively controlled
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Genes controlled negatively by repressor proteins are not transcribed due to the presence of the repressor proteins
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How are genes positively controlled
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Genes controlled positively by activator proteins require the presence of activator proteins in order to initiate transcription
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What does lacZ encode
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Beta-galactosidase, which hydrolyzes the bond between the lactose sugars
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What does lacY encode
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Beta-galactoside permease, which brings lactose into the cell
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What does lacA encode
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Beta-galactoside transacetylase (function unknown)
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How is repression of the lac operon relieved
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By the addition of an inducer that binds to the repressor protein, alters the conformation of the repressor, and thereby reduces the affinity of the repressor for the operator
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How is the synthesis of biosynthetic enzymes repressed
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By the presence of end product. The repressor protein is inactive in the absence of the end product effector
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What is required for initiation of transcription at the lac promoter
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cAMP together with cAMP receptor protein (CRP or CAP)
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In bacteria, where is the regulation of protein synthesis primarily
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At the level of transcription rather than translation
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What is the difference between end product repression of enzyme synthesis versus inhibition of enzyme activity
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Repression of enzyme synthesis is concerned with the economy in macromolecular synthesis. Inhibition of enzyme activity is concerned with the economy in metabolite synthesis
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What does transcription termination at the end of a cistron or an operon involve
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A termination sequence, RNA polymerase, and rho factor
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How does secondary structure of mRNA play an important role in attenuation
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The leader peptide is followed by a transcription termination sequence. The mRNA can have two alternative conformations based on binding to the leader peptide
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In translational control, what is the correct start codon in the mRNA preceded by
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The Shine-Dalgarno (SD) sequence. The SD site must be free for translation to occur
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What is the SOS repair pathway
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A repressor, encoded by the lexA gene, reduces expression of numerous genes involved in DNA repair. In reponse to DNA damage, the recA protein is activated, which cleaves the lexA repressor, allowing transcription of the repair proteins
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Besides the lexA repressor, what else does the recA protease cleave
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The lambda repressor, as well as repressors of several other lambda related phages
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What does the two-component signal transduction system consist of
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A sensor kinase in the membrane, and a Response regulator in the cytoplasm
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What is quorum sensing
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Defines an environmental sensing system that allows bacteria to monitor their own population density
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What signaling molecules do gram positive bacteria use for quorum sensing
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Peptides. Gram negative use Acyl homoserine lactones
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