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78 Cards in this Set
- Front
- Back
Archibald Garrod
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One gene - one enzyme
Alkaptonuria - enzyme metabolism of alkaptans |
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Beadle and Tatum
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Proved One gene - one enzyme hypothesis -Bread Mold mutations
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Central Dogma
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DNA -> RNA -> Protein
Transcription Translation |
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Transcription
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RNA synthesis under the direction of DNA in nucleus
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Translation
(Eukaryote) |
Polypeptide synthesis under the direction of mRNA at the ribosome(s) in the cytoplasm
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Gene
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programs protein synthesis via genetic messages in the form of messenger RNA
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Exon
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Expressed nucleic acid sequences
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Intron
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Intervening nucleic acid sequences
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Codon
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Triplets of nucleotides that represent a single amino acid
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Mutagen
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Physical and chemical agents that cause DNA mutation
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RNA processing
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modification of preMessenger RNA before genetic messages are passed to the cytoplasm
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Anti-codon
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nucleotide triplet on tRNA which base pairs with complementary codon on mRNA
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Promotor
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The DNA sequence where RNA polymerase attaches and initiates transcription
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Transcription Factors
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a collection of proteins that mediate the binding of RNA polymerase and initation of transcription
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Primary Transcript
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Initial RNA transcript for any gene (includes expressed and intervening sequences)
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Three stages of Transcription
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1. Initiation
2. Elongation 3. Termination |
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Metabolic Pathway
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Cells synthesize and degrade most organic chemicals by sequences of reactions that are catalyzed by enzymes
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One gene - One Polypeptide
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Restatement of one gene one enzyme or one gene one protein
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Alkaptonuria
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A rare genetic inability to make the enzyme that metabolizes Alkapton
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messenger RNA (mRNA)
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carries genetic message specifying amino acid sequences from the DNA in the nucleus to the protein–synthesizing machinery (ribosomes) in the cytoplasm
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Ribosome
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Eukaryote Translation
coordinate the sequential coupling of tRNA molecules to mRNA codons |
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Start codon
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where translation initiates
AUG |
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Stop codon
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where translation terminates
UAA UAG UGA |
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transfer RNA (tRNA)
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cloverleaf-shaped structure which carries the appropriate amino acid to the ribosome
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Two methods of post-transcriptional modification
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1. Alternation of mRNA ends
2. Splicing |
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Template strand
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Strand of DNA that provides the template for ordering the sequence of nucleotides in an RNA transcript
NOTE: only one of the two DNA strands is transcribed. |
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5' Cap
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a modified guanine nucleotide is added to the 5’ end of the transcript
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3' Poly-A Tail
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50-250 adenine nucleotides are added to the 3’ end of the transcript by poly-a polymerase (enzyme)
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Purpose of end modification
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1.Help export mature mRNA out of nucleus
2. Protect mRNA from degradation by hydrolytic enzymes 3. Help ribosomes attach to the mRNA |
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Why Splicing?
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removes intervening sequences (introns) from the mRNA transcript
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Why splicing ? 2
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1. One gene can encode more than one polypeptide
2. Gets rid of evolutionary “junk DNA” |
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Exon Shuffling (1)
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giving more room for crossover events between exons may increase chances for formation of beneficial new proteins,
NOTE: sexual traits in flies |
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Reading frame
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The way a cell′s mRNA–translating machinery groups the mRNA nucleotides into codons
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Triplet code
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A set of three–nucleotide–long words that specify the amino acids for polypeptide chains.
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transcription initiation complex
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The completed assembly of transcription factors and RNA polymerase bound to the promoter.
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TATA box
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A promoter DNA sequence crucial in forming the transcription initiation complex.
a nucleotide sequence contain "TATA" about 25 nucleotides upstream from transcription start point |
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RNA polymerase II
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used for mRNA synthesis in eukaryotes.
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sliceosome
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A complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron and joining the two adjacent exons.
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Ribozyme
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An enzyme–like RNA molecule that catalyzes reactions during RNA splicing
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domains
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1. discrete structural and functional regions of a protein
2. correspondence to exons splicing |
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Exon shuffling (2)
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allows for creation of proteins with multiple polypeptides and multiple structural and functional domains
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aminoacyl–tRNA synthetase
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An enzyme that joins each amino acid to the correct tRNA
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aminoacyl–tRNA
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An "activated amino acid"
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wobble
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A relaxation of the base–pairing rules so
third nucleotide of a tRNA anticodon can form hydrogen bonds with more than one kind of base |
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Ribosomal RNA (rRNA)
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Plays catalytic (ribozymes) and structural roles in the ribosome.
Created in nucleolus |
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P-Site
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holds the tRNA carrying the growing polypeptide chain
NOTE: peptidyl–tRNA site |
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A-Site
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holds the tRNA carrying the next amino acid to be added to the chain
NOTE:aminoacyl–tRNA site |
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E-Site
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place where discharged tRNAs leave the ribosome.
NOTE: EXIT site |
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Three stages of Transcription
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1. Initiation
2. Elongation 3. Termination |
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Transcription Initiation
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1. RNA Polymerase binds to the promoter
2. DNA strands unwind 3. RNA synthesis initiates at the start point of template strand |
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Transcription Elongation
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1. RNA polymerase:
a.continues to untwist the double helix, b. adds nucleotides to the 3′ end of the growing RNA molecule 2. the new RNA molecule peels away from its DNA template 3. DNA double helix re–forms |
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Transcription Termination
(Eukaryote) |
the polymerase transcribes a sequence on the DNA called the polyadenylation signal sequence, which codes for a polyadenylation signal (AAUAAA) in the pre–mRNA
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Three stages of Translation
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1. Initiation
2. Elongation 3. Termination |
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Translation Initiation
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1.small ribosomal subunit binds to both mRNA and a specific initiator tRNA
2.The small subunit then scans, downstream for the start codon |
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Translation Elongation
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1. Codon Recognition
2. Peptide Bond formation 3. Translocation |
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Translation Termination
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stop codon in the mRNA reaches the A site of the ribosome
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Polysome
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An aggregation of several ribosomes attached to one messenger RNA molecule
NOTE: Polyribosome |
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post–translational modifications
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may be required before the protein can provide a specific function in the cell
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Bound ribosomes
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make proteins of the endomembrane system (the nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane) as well as proteins secreted from the cell
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Free ribosomes
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suspended in the cytosol and mostly synthesize proteins that dissolve in the cytosol and function there
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signal peptide
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A stretch of amino acids on a polypeptide that targets the protein to a specific destination in a eukaryotic cell
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signal–recognition particle (SRP)
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A protein–RNA complex that recognizes a signal peptide as it emerges from the ribosome
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translocation complex
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protein complex that has membrane pore and signal-cleaving enzyme
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RNA is multifunctional - Why?
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RNA:
1. Can hydrogen–bond to other nucleic acid molecules. 2. can assume a specific conformation by forming hydrogen bonds between bases in different parts of its own polynucleotide chain. 3. has functional groups that allow it to act as a catalyst (ribozyme). |
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Small nuclear RNA (snRNA)
SNURPs |
structural and catalytic roles in sliceosomes
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SRP RNA
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component of signal recognition particle (SRP)
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Small nucleolar RNA (snoRNA)
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aids in processing of pre-RNA transcripts for ribosome subunit formation in the nucleolus
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small interfering RNA (siRNA) and microRNA (miRNA)
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involved in regulation of gene expression
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Mutation
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A change in the DNA of a gene, ultimately creating genetic diversity
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Point Mutation
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A change in a gene at a single nucleotide pair
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Genetic disease or disorder
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a mutation that has an adverse effect on the phenotype of an organism
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base-pair substitution
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the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides
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base-pair substitution of third codon
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No effect to organisms Phenotype - rules are relaxed - wobble
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Missense mutation
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a base–pair substitution in which the new codon still codes for an amino acid
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Nonsense mutation
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A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein
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Insertion mutation
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A mutation involving the addition of one or more nucleotide pairs to a gene
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Deletion mutation
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A mutation involving the deletion of one or more nucleotide pairs to a gene
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Frameshift mutation
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number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the following nucleotides into codons
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