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67 Cards in this Set
- Front
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name for coding regions of dna
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genes
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how strands of dna run
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anti parallel. if one strand rusn 3'-5-, the other runs 5'-3'
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number of bonds between a and t
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two
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number of bonds between c and g
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three
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reason dna strands can't both run the same direction (5'-3' and 5'-3')
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won't allow the bases to be near each other to hydrogen bond
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mRNA
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messenger rna, the rna used to make a protein (base for coding)
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tRNA
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"tugboat" rna, participates in translation by matching correct anitcodon/amino acid
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rRNA
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ribosomal rna
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job of rna polymerase
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to transcribe dna into rna
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initiation in prokaryotes
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rna poly recognizes promoter sequence (through induced fit), rna binds to promoter, dna is unwound to stard (hydrogen bonds broken)
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where rna binds and where rna starts (promoter sequence in prokaryotes)
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-35, then -10, then +1, also there is no 0
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where eukaryotic promoter sequence is
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-75, -25, +1
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in order for rna polymerase to recognize promoter sequence, rna poly must
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be correct sequence of bases (small change okay), be correctly spaced
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elongation
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process of building rna strand, rna poly matches complementary nucleotides to the DNA template strand
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template strand
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the actual strand rna polymerase uses to build rna
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coding (nontemplate) strand
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not used for building rna, but has same sequence as rna except ts are replace w/ us
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how rna poly transcibes (direction)
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5'-3'
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termination
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how transcription ends, long strand of ts and as
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why as and ts cause termination
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they only have 2 h bonds between them, whereas cg has 3, 2 h bonds not enough to hold dna template and rna together
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translation
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using rna code to create a protein
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where translation occurs for prokaryotes
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in the cytoplasm or the rough er
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how many nucleotides/codon
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3 bases
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job of tRNA
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brings correct amino acid to match with the mRNA codon
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what each tRNA holds
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an anticodon (complementary to the mRNA strand) with a corresponding amino acid
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what ribosomes are made of
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an rRNA and a protein
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job of ribosome
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workbench for translatipon-it holds the mRNA and tRNAs in the correct position to assemble the protein
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3 sites on ribosome
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a site=where tRNA first binds to mRNA, p site=where the amino acid is added on to the polypeptide chain, e site=exit site
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where translation begins
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at the start codon aug/methionine (not same as +1!!)
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what ribosome does during translation
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breaks bond between tRNA and amino acid, creates a new peptide bond to link it to the polypeptide chain
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how does mRNA know if it is correctly matched to the tRNA
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hydrogen bonding between the bases
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how translation is stopped
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when a stop codon is reached (UAA, UAG, UGA), release factor binds to the mRNA, breaking apart the ribosome and mRNA/protein
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first step in rna processing
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1. modified g nucleotide added to the 5' end of pre mRNA to help mRNA bind to ribosome
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second step in rna processing
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2. poly a tail added to 3' end of premRNA, helps direct mRNA out of the nucleus
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third step in rna processing
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3. splicing--introns (noncoding regions) cut out, exons pieced together, done compeletely by enzymes
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point mutation
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single nucleotide subsituted/inserted
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base pair substitution
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replacement of one nucleotide and its partner
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missense mutation
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dna codes for one different amino acid (can have no effect if amino acid still has same properties)
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nonsense mutation
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early stop codon introduced, protein is incomplete
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insertion/deletion
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base pair deleted, changes reading frame, disastrous!!! changes everything
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frameshift
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changes reading frame, will almost always result in the wrong/nonfunctioning protein
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how proteins know where to go
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secretory proteins have molecular tags called signal peptides (the first amino acid translated) that directs protein through the er
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signal peptide
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sequence of amino acids at beginning of protein that binds to signal recognition protein(srp)
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srp
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signal recognition protein
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how srp and signal peptide work to direct
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they bind together, then the two bind to a receptor on the er, protein fed into er and the signal sequence is removed by an enzyme inside the ER
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gene expression
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transcribing and translating a gene
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how regulation affects an organism
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allows organism to selectivley transcribe/late to prevent too little/too much of one protein
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genes expressed depend on
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the type of cell or the particular needs of the cell at the time
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operon
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group of related genes
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basic structure of operon
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promoter sequence at the very beginning, all of the genes will be transcribed together in one long strand of rna
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benefit of organizing genome into operons
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more efficient, transcribes everything needed for a process at once
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repressible operon
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operon usually on, but can be inhibited
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regulatory gene
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found somewhere else on genome, not part of operon, code for a repressor
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coprepressor
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when binds to repressor it becomes active
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how repressor protein is transcribed
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in its inactive form
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operator region
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just after promoter region, repressor can bind to operon if repressor is in active form
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when transcription is "on" (lack of needed protein) in an repressible
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repressor is inactive, rna poly is able to bind to promoter to transcribe the gene
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when trasncription is "off" (sufficient amount of protein)
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the protein binds to the repressor, converting it to active form, blocking rna poly from transcribing
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under what conditions would inducible operon go from "off" to "on"
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when there is lack of the needed protein
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operator region
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just after promoter region, repressor can bind to operon if repressor is in active form
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when transcription is "on" (lack of needed protein) in an repressible
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repressor is inactive, rna poly is able to bind to promoter to transcribe the gene
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when trasncription is "off" (sufficient amount of protein)
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the protein binds to the repressor, converting it to active form, blocking rna poly from transcribing
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under what conditions would inducible operon go from "off" to "on"
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when there is lack of the needed protein
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inducible operon
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operon is usually off
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how inducible repressor is translated
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as active
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when regulatory gene is bound by inducer, it becomes inactive
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since there is enough protein, the is no need to express the operon
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how transcription factors help rna poly bind
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creates an area that chemically attracts rna poly
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enhancer sequence
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far away from gene it transcribes, activator molecules bind to enhancer sequence, enhancer loops aroudn so that the activators can also bind to transcription factors, all cause rna poly to start
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