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21 Cards in this Set
- Front
- Back
how is gene expresion controlled by regulating transcription?
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binding protein to regulatory sequence blocks transcription by getting in the way of rna polyermase, or stimulates transcrip. by facilitating binding rna polyermase to the promoter
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what is transcriptional control in prokaryotes?
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adjusts cell's activities to immmediate, external environment to grow and divide as rapidly as possible
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what is transcriptional control in eukaryotes?
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-most common
-primary funct. is maintaining gene control -compensate for physiological cnages or mediate product, decisions |
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what is posttranscriptional control?
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influencing mRNA produced from genes or the activity of proteins encoded by the mRNA
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what is a major groove?
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-proteins can bind to outside surface of double helix
-nucleotides' hydrophobic methyl groups, hydrogen atoms, and hydrogen bond donors & acceptors protrude from major groove -employ bends in protein chain that permit interlocking w/major groove (dna-binding motifs) |
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describe the helix-turn-helix motif.
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-one helical segment fits snuggly in major groove, other butts against outside of dna molecule
-two binding sites doubles contact zone and greatly strengthens the bond |
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describe the homeodomain motif.
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-special kind of helix-turn-helix motif surrounded by region initiating key develop. stages
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describe the zinc finger motif.
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-zinc atoms coordinate dna binding
-the more zinc fingers in cluster, the stronger the protein binds to dna |
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describe the leucine zipper motif.
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-formed when region on one subunit containing several hydrophobic amino acids interacts w/similar region on another subunit
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what is a lac operon?
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multi. genes are part of a single gene expression unit.
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what do basal transcription factors do?
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they are necessary to eestablish productive initiation; do not increase the rate
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what do specific transcription factors do?
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they act in a tissue-or time-dependent manner to stimulate higher levels of transcription than the basal levels
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what are enhancers?
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binding site of specific transcription factors;accomplished by dna bending to form a loop, positioning the enhancer close to the promoter
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why is transcriptional control more complicated in eurkayotes than in prokaryotes?
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-dna organized in chromatin
-transcrip. occurs in nuclues & translat. in cytoplasm -complex developm. programs -multiple tissue types |
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what is one effect of chromatin structure on gene expression?
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promoter blocking by nucleosomes
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what does dna methylation do?
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blocks accidental transcription of "turned off" genes
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what does posttranscriptional control on eukaryotes involve?
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invovles the recognition of specific sequences on primary rna transcript. by regulatory proteins and small rna molecules
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how does rna interference work?
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gene silencing happens when a change in gene expression is passed from one generation to another; appears to play a major role in epigenetic change
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what is alternative splicing?
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exons can be spliced together in dif. ways to assemble a variety of polypeptides
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describe the transport of the transcript out of the nucleus.
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passage out of mRNA transcript across nuclear membrane requires the transcript to be recognized
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what do translation repressor proteins do?
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shut-down translation by binding to the beginning of the transcript so that it can't attach to the ribosome
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