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32 Cards in this Set
- Front
- Back
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Nucleotide
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sugar (deoxyribose or ribose) with a phosphate group
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purines
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double ringed
- adenine, guanine |
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pyrimidines
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single ring
- cytosine, thymine CUT the PIE = Cytosine, Uracil, and Thymine are PYrimidines |
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DNA base pairing
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- amount of A = amount of T
- amount of C = amount of G Higher G/C content = more tightly bound the strands are |
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DNA
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- double-stranded helix
- nucleotides = sugar (deoxyribose) + phosphate + nitrogenous base (A, T, C, G) - Complementary base pairing (A/T, C/G) - Strands are antiparallel: 5' end of one strand paired with 3' of other strand - found in nucleus only |
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RNA
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- single-stranded
- sugar = ribose - Base pairing: A/U, G/C - Found in nucleus and cytoplasm |
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mRNA
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carries complement of DNA sequence and transports it from nucleus to ribosomes for protein synthesis
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monocistronic
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one mRNA strand codes for one polypeptide
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tRNA
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- in cytoplasm
- aids translation of mRNA |
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rRNA
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- structural component of ribosomes and most abundant
- made in nucleolus |
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hnRNA
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- heterogeneous nuclear RNA
- ribonucleoprotein complex that is the precursor for mRNA |
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Transcription
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DNA to RNA
Requires: - RNA polymerase - Promoter - Termination sequence |
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Post-transciptional RNA processing
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exons (coding) and introns (non-coding)
- introns are removed and exons are spliced to form mature mRNA - processing occurs in nucleus |
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degeneracy
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accounts for the fact that a mutation in DNA does not always result in an altered protein
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stop codons
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UAA
UAG UGA |
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aminoacyl-tRNA
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- each aa has own
- has active site that binds both aa and corresponding tRNA, catalyzing their attachment to form aminoacyl-tRNA complex - requires ATP |
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P site
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peptidyl-tRNA binding site
- binds to tRNA attached to growing polypeptide chain |
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A site
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aminoacyl-tRNA complex binding site
- binds incoming aminoacyl-tRNA complex |
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1) DNA --> DNA
2) DNA --> RNA 3) RNA --> protein |
1) replication (new DNA made in 5' to 3' direction)
2) transcription (new RNA made in 5' to 3' direction) 3) translation (mRNA read in 5' to 3' direction) |
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DNA containing viruses
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- viral DNA replicated
- viral mRNA transcribed using host machinery in nucleus - some viruses must bring their own DNA and RNA pol (if they replicate and transcribe in cytoplasm) |
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RNA containing viruses
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- viral RNA replicated and transcribed in cytoplasm
- RNA replicase transcribes new RNA to RNA template - some viruses bring RNA replicase with them, or part of viral RNA functions as mRNA for making RNA replicase |
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retroviruses
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- use RNA as a template for DNA (rather than RNA)
- use reverse transcripase to do this |
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provirus or prophage
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Viral DNA intergrated into host chromosome
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polycistronic
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mRNA coding form more than one polypeptide
- found in prokaryotes |
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transformation
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foreign chromosome fragment incorporates into host chromosome via recombination
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conjugation
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donor and recipient connect via sex pili to transfer F-factor
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Hfr cells
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high frequency of recombination
- transfered genes recombine with genome of recipient cells |
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transduction
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fragements of chromosome are packaged into viruses
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operon
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- for gene regulation
- consists of: operator gene, promotor gene, regulator gene (and inducer in inducible systems) |
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inducible system
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- represor binds to operator, preventing RNA polymerase from binding and transcribing genes
- repressor is active until it binds to the inducer - For transcription to occur: inducer must bind to the repressor |
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inducible system (summary)
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- RNA pol binds to promotor = transcription occurs
- Repressor binds to operator = NO transcription - Inducer binds to repressor = no binding to operator = transcription occurs |
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repressible system
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- repressor is inactive until a it combines with a corepressor which can then bind to operator and prevent transcription
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