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54 Cards in this Set
- Front
- Back
promoter
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site where RNA polymerase initially binds to DNA
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initiation
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first stage of transcription; requires a promoter
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transcription factors
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bind to the promoter during transcription; these proteins facilitate binding of RNA polymerase to the site
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transcription initiation complex
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completed assembly of transcription factors and RNA polymerase at the promoter region
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elongation
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RNA polymerase continues building the RNA strand ; the newly synthesized RNA strand easily separates from the DNA and the DNA molecule “zips up” behind RNA polymerase, reforming the double helix
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termination
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the end of RNA transcription
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codons
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sequences of three bases that instruct for the addition of a particular amino acid (or a stop) to a polypeptide chain;
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triplet code
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a 3-base code
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stop codons
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do not code for an amino acid but instead will end the protein chain
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coding region
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codes for protein synthesis
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leader sequence
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the mRNA strand prior to the start codon is called the 5’ untranslated region or this
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trailing sequence
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the mRNA strand after the stop codon is called the 3’ untranslated region or this
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Translation
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using information in mRNA to direct protein synthesis
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ribozyme
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catalyzes peptide bond formation
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anticodon
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each tRNA has this region that will form a proper complementary basepairing with a codon on an mRNA molecule
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aminoacyl-tRNA synthetases
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tRNA is linked to the appropriate amino acid by enzymes called these; the result is aminoacyl-tRNA.
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E site
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where uncharged tRNA molecules are moved and then released
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P site
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where the completed part of the polypeptide chain will be attached to tRNA
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A site
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where the new amino acid will enter on an aminoacyl-tRNA as a polypeptide is made
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initiation of translation
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start of polypeptide production
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initiator tRNA
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recognizes the codon AUG, which is the initiation start codon
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ribosome recognition sequence
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where small ribosomal subunit binds to an mRNA in a prokaryote
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initiation factors
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proteins that help the small subunit bind to the initiator tRNA and mRNA
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elongation in translation
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the addition of amino acids to the growing polypeptide chain
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elongation factors
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assist in getting the charged tRNA to bind
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translocation
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takes place after elongation in translation; moving amino acids and nucleotides from the A site to the P site to the E site.
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termination in translation
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last step of translation where a stop codon signals the end for translation
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termination factor
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the termination factor causes everything to dissociate, freeing the polypeptide, mRNA, last tRNA, and ribosomal subunits all from each other
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polyribosomes
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as many as 20 ribosomes may be synthesizing protein from the same message - these are called what?
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5’ cap
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required for binding to eukaryotic ribosomes; makes eukaryotic mRNAs less susceptible to degradation and to promote the transport of the mRNA out of the nucleus
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polyadenylation
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the 3’ tail in RNA
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polyadenylation signal
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signals for the addition of a “tail” on the 3’ end of the mRNA
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poly-A tail
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the mRNA tail is a series of adenines called this
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introns
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stretches of bases that “interrupt” the sequence and must be removed
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exons
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regions that will not be removed from the sequence because they do not "interrupt" it
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RNA splicing
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the process of removing introns
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snRNPs
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made of small RNA molecules and proteins; associate with the mRNA in a complex called the spliceosome
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spliceosome
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catalyzes cutting out and removing an intron and joining together the exons
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alternative RNA splicing
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allows one DNA sequence to direct synthesis of two or more different polypeptides
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domain
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a region within the protein that has a specific function
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exon shuffling
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proteins consist of such functional domains which can be readily shuffled around during evolution to produce new proteins with novel catalytic functions
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Mutations
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changes in the DNA sequence
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mutagens
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DNA-damage inducers
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carcinogens
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mutagens that increase the likelihood of cancer
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mutational hot spots
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DNA regions that are more prone to mutations
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point mutations
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base substitution mutations; mutations that result in the substitution of one base for another
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silent mutation
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if the point mutation does not actually cause a change in what amino acid is coded for, it is called this
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missense mutation
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if the point mutation causes a change in what amino acid is coded for, it is called this
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nonsense mutation
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if the point mutation results in the formation of a stop codon where an amino previously was coded for, it is called this
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transposon
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some mutations are caused by pieces of DNA that can jump around the genome; such jumping DNA is called this.
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constitutive genes (housekeeping genes)
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genes that are constantly transcribed, with little or no regulation
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repressors
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transcription factors that suppress or stop gene expression
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activators
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transcription factors that either activate ( “turn on”) gene expression, or to enhance gene expression
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enhancers
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DNA regions, often far from the promoter, where activators will bind either directly or indirectly
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