Term
| transcription and translation can occur _________ in bacteria b/c ______ |
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Definition
| simultaneously; no nuclear envelope to separate the two processes |
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Term
| in eukaryotes, RNAs processed in ____ and mRNAs exported to _______ |
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Definition
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Term
| once mRNAs out of nucleus, ______ attach to them and begin _____ |
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Definition
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Term
| in eukaryotes, transcription and translation occur ____ |
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Definition
| at different times in different places |
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Term
| 6 things that have to be present for translation to occur |
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Definition
| ribosomes (catalytic machinery), mRNA (message to be translated), amino acids (building blocks of proteins), ATP & GTP (energy to drive endergonic polymerizations that form proteins), and tRNA |
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Term
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Definition
| acts as interpreter in translation process; serves as chemical go-between that allows amino acids to interact with mRNA template; short 75-85 nucleotides |
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Term
| secondary structures of tRNA |
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Definition
| some of the bases can form hydrogen bonds with complementary bases in a different region of the same molecule, forming a cloverleaf shape - CCA sequence at 3' end offers binding site for amino acids; triplet on loop on opposite end of cloverleaf serves as anticodon; cloverleaf structure folds over to produce an L-shaped molecule (tertiary structure); o all of the tRNAs in a cell have the same L-shaped structure, but each has a distinct anticodon and attached amino acid; tertiary structure results in precise separation between anticodon and attached amino acid |
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Term
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Definition
| a tRNA that becomes covalently linked to an amino acid |
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Term
| aminoacyl tRNA synthetase |
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Definition
| attach amino acids to tRNAs; for each of the major 20 amino acids, there is a different aminoacyl tRNA synthetase and one or more tRNAs |
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Term
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Definition
| set of three ribonucleotides that forms base pairs with mRNA codon |
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Term
| during translation, ribosome _____ |
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Definition
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Term
| ribosome binding site/Shine-Dalgarno sequence |
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Definition
| six nucleotides upstream from AUG start codon; consists of all or part of the bases 5’-AGGAGGU-3’ |
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Term
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Definition
| proteins that mediate interaction between small subunit and the message; in eukaryotes, bind to 5’ cap on mRNAs and guide it to the ribosome |
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Term
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Definition
| occurs when ribosome moves down mRNA through in 5’ -> 3’ direction; moves empty tRNA into E site; moves tRNA with growing polypeptide into P site; opens A site and exposes a new mRNA codon; if E is occupied, tRNA ejected into cytosol |
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Term
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Definition
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Term
| ____ and ____ affect frequency of crossing over and how certain genes are turned on or off |
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Definition
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Term
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Definition
| single base change (if DNA polymerase inserts wrong base as synthesizing DNA, and proofreading fails, a change in sequence of bases in DNA results) |
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Term
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Definition
| type of alteration in base sequence that has no effect at all; if in third position will probably code for same amino acid; are neutral in their effect on individual's fitness; possible for point mutations to be silent and neutral b/c of genetic code redundancy |
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Term
| missense mutations/replacement mutations |
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Definition
| point mutations that cause changes in amino acid sequence of proteins; often are deleterious; may also be beneficial (people with one mutant gene have malaria resistance) |
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Term
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Definition
| reduce an individual's fitness |
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Term
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Definition
| change in number of each type of chromosome |
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Term
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Definition
| involves addition or deletion of a chromosome |
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Term
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Definition
| chromosome segment flips and reattaches to same chromosome |
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Term
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Definition
| chromosome segment detaches and attaches to a different chromosome |
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Term
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Definition
| strings of ribosomes; presence can quicken overall pace of protein production; observed routinely in both bacteria and eukaryotes |
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Term
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Definition
| protein that fits tightly into A site because their size, shape and electrical charge are tRNA-like; don’t carry an amino acid, though |
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Term
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Definition
| in some bacteria, bind to ribosome near “tunnel” where growing polypeptide emerges from ribosome; suggests that folding occurs as polypeptide is emerging from ribosome |
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Term
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Definition
| (1) arrival of aminoacyl tRNA (2) peptide bond formation (3) translocation |
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Term
| ________ bond formation one of most important reactions b/c making proteins so important |
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Definition
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Term
| at start of elongation, ______ |
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Definition
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Term
| summary of initiation in bacteria |
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Definition
| (1) mRNA binds to small subunit of ribosome (2) initiator aminoacyl tRNA bearing f-Met binds to start codon (3) large subunit of ribosome completes the complex |
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Term
| initiation of translation is complete when ______ |
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Definition
| large subunit joins the complex |
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Term
| initiation of translation always occurs at __________ |
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Definition
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Term
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Definition
| has an anticodon; has amino acids covalently attached |
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Term
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Definition
| specifies the amino acid sequence for a protein; contains exons |
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Term
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Definition
| is a component of ribosomes; is the most abundant form of RNA |
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Term
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Definition
| are not used in protein synthesis; only needed to initiate a new strand of DNA during DNA replication |
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Term
| three things to remember when predicting mRNA sequence |
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Definition
| (1) RNA polymerase reads sequence from only template strand (2) in the 3' to 5' direction and thus produces the mRNA strand in the 5' to 3' direction (3) but U instead of T |
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Term
| Which of the following initially determines which DNA strand is the template strand, and therefore in which direction RNA polymerase II moves along the DNA? |
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Definition
| the specific sequence of bases along the DNA strands |
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Term
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Definition
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Term
| During RNA processing a _____ is added to the 5' end of the RNA |
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Definition
| modified guanine nucleotide (the 5' cap consists of a modified guanine nucleotide) |
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Term
| During RNA processing a _____ is added to the 3' end of the RNA |
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Definition
| long string of adenine nucleotides (poly-A tail) |
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Term
| Proteins that will ultimately function in the cytoplasm (like PFK) are translated on ______ |
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Definition
| free cytoplasmic ribosomes and released directly into the cytoplasm |
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Term
| Proteins that are destined for the membranes or compartments of the endomembrane system, as well as proteins that will be secreted from the cell (insulin, for example), are translated on _____ |
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Definition
| ribosomes that are bound to the rough ER |
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Term
| the initiator tRNA binds to the ribosome's __site |
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Definition
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Term
| What feature ensures that the correct amino acid is added with reading of a specific codon during translation? |
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Definition
| the anticodon of a properly formed aminoacyl tRNA |
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Term
| during elongation, site in the ribosome where a codon is being read |
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Definition
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Term
| order of elongation in prokaryotic translation |
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Definition
| (1) Binding of mRNA with small ribosomal subunit (2) Recognition of initiation codon (3) Complementary base pairing between initiator codon and anticodon of initiator tRNA (4) Attachment of the large subunit (5) Base pairing of the mRNA codon following the initiator codon with its complementary tRNA |
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Term
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Definition
| mutation that results in premature termination of translation |
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Term
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Definition
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Term
| discovered amino acids are transferred from ________ to ________ |
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Definition
| aminoacyl tRNAs; proteins |
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Term
| many amino acids specified by more than one codon & codons for the same amino acid tend to have ______ |
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Definition
| same nucleotides at first and second position and then a different nucleotide at third position |
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Term
| Crick's wobble hypothesis |
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Definition
| inside the ribosome, tRNAs with nonstandard base pairing at third position of codon can still bind successfully to an anticodon; nonstandard base pairing allowed as long as it doesn’t change amino acid for which it codes; the wobble in third position allows 40 tRNAs to bind to all 61 mRNA codons |
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Term
| conversion begins when _______ |
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Definition
| anticodon of a tRNA that carries an amino acid binds to codon in mRNA |
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Term
| conversion is complete when ________ |
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Definition
| a peptide bond forms between that amino acid and the growing polypeptide chain |
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Term
| large subunit of ribosome |
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Definition
| where peptide bond formation takes place |
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Term
| small subunit of ribosome |
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Definition
| holds mRNA in place during translation |
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Term
| small and large subunits of ribosome both consists of _______ |
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Definition
| complex of RNAs and proteins |
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Term
| during protein synthesis, three distinct tRNAs _________ |
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Definition
| are lined up inside ribosome; all three are bound to their corresponding mRNA codon at base of the structure |
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Term
| tRNA on right, middle and left in translation |
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Definition
| right carries an amino acid (site A - acceptor); middle holds growing polypeptide chain (site P - peptide bond formation); left no longer has an amino acid attached and is about to leave ribosome (site E - exit) |
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Term
| ribosome synthesizes proteins in three steps |
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Definition
| (1) aminoacyl tRNA diffused into site A; its anticodon binds to a codon in mRNA (2) peptide bond forms between amino acid held by aminoacyl tRNA in site A and growing polypeptide, which is held by a tRNA at site P (3) ribosome moves ahead and all three tRNAs move one position down the line; protein that is being synthesized grows by one amino acid each time this three-step sequence repeats |
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Term
| protein synthesis starts at ______ and proceeds to _________ |
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Definition
| amino-end (N-terminus); carboxy end (C-terminus) |
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Term
| to translate mRNA, ribosome must _____ |
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Definition
| begin at a specific point in message (initiation), translate up to termination codon (elongation) and stop (termination) |
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Term
| remember that a start codon found ________ (true in both bacteria and eukaryotes) |
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Definition
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Term
| initiation of translation begins when _____ |
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Definition
| a section of rRNA in small subunit binds to complementary sequence on mRNA (called ribosome binding site/Shine-Dalgarno sequence) |
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Term
| second step in initiation of translation |
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Definition
| aminoacyl tRNA with a modified form of methionine (N-formylmethionine) binds to AUG start codon |
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Term
| when ribosome is completely assembled in translation, _____ |
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Definition
| tRNA bearing f-met occupies the P site |
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Term
| elongation of translation proceeds when ______ |
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Definition
| aminoacyl tRNA binds to the codon in A site via complementary base pairing between anticodon and codon |
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Term
| elongation of translation: when a tRNA occupies both P and A sites, _______ |
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Definition
| amino acids they hold are placed in ribosome’s active site (where peptide bond formation, the essence of protein synthesis, occurs) |
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Term
| each elongation cycle depends on ____________ |
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Definition
| an input of energy from several GTP molecules and elongation factors |
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Term
| protein synthesis is catalyzed by _____ |
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Definition
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Term
| active site consists completely of ______ |
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Definition
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Term
| start of termination of translation |
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Definition
| when translocation opens A site and exposes one of the stop codons, release factor fills A site |
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Term
| steps after start of termination of translation |
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Definition
| active site catalyzes hydrolysis of bond linking tRNA in P site with polypeptide chain; this frees polypeptide from ribosome, ribosome separates from mRNA, and two ribosomal subunits dissociate; subunits now ready to attach to start codon of another message and start translation again |
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Term
| proteins _______ after termination |
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Definition
| not fully formed and functional |
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Term
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Definition
| during elongation, long before termination - spontaneous but is sped up by molecular chaperones |
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Term
| ways proteins are modified post-translation |
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Definition
| small chemical groups may be added in rough ER and Golgi apparatus; some proteins get sorting signal that serves as an address; some are augmented with sugar or lipid groups critical for normal function |
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Term
| many proteins lose or gain phosphate group in post-translational modifications |
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Definition
| may cause major changes in shape and chemical reactivity of proteins since phosphate group has two negative charges; can switch it from active to inactive or vice versa |
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Term
| example of point mutations being transcribed and translated |
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Definition
| hemoglobin protein made of four polypeptides – two copies of α-globin and β-globin; single change in primary structure causes protein to crystallize when oxygen levels in blood are low, causing sickle cells |
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