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mRNA-
tRNA-
Aminoacyl tRNA synthetase-
Ribosome (rRNA and proteins)- |
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tRNA- brings the AA to the code
Codon specific
Each AA has at least one type of tRNA assigned to it, most have several tRNAs |
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Term
| Aminoacyl tRNA synthetase |
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Definition
| Aminoacyl tRNA synthetase- adds the AA to the tRNA |
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Term
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Definition
Ribosome (rRNA and proteins)- the “work-horse”
Machine” compromised of RNA and proteins
Large subunit- peptidyltransferase (by rRNA) activity
Small subunit- tRNA binding site
Works at about 20AA/sec (Prok) and 2-4AA/sec (Euk)
A=Aminoacylated-tRNA site
P=Peptidyl-tRNA site
E=Exite site |
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Term
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Definition
DNA region that codes for a polypeptide
(ORF) |
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Definition
The structure of tRNA dictates the enzyme
Knows which AA to use by steric hindrance
Importance?
Energy
Correct codon |
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Definition
Done by aminoacyl tRNA synthetase
Very precise, errors are less than 0.1%
Once the tRNA is charged, no “fixing” system in place
Misincorporated AA can lead to change in AA/protein
Affects a single protein |
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Term
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Definition
Degeneracy
Wobble-base pairing
Synonymous codons |
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| Degeneracy of Genetic Code |
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Definition
| More than one tRNA per AA and a tRNA can pair with more than one codon which leads to… |
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Definition
| Why so many of the alternative codons for AA differ only in their third nucleotide |
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| They both translate the same AA |
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Codons are read in the 5’ 3’ direction
Codons are non-overlapping
Message is translated in a fixed reading frame |
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Tetracycline:
Target: "A" site of 30S subunit
Consequence: Inhibits aminoacyl-tRNA binding to "A" site |
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Bonds form in the C-terminus
Energy driven
Peptide moves from peptidyl-tRNA aminoacyl-tRNA |
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Code altering
Missense
Non-sense/stop
Frame-shift
Non-code altering |
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Definition
| One gene mutation reverses another gene’s mutation |
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Definition
| The mutation occurs in the same gene, close to the first codon’s mutation |
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Term
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Definition
Extracellular signals control genes
Such as the growth environment
Activators and repressors often regulate transcription initiation
Activators= positively
Repressors= negatively
Alternative sigma factors can also control transcription
Binding of RNAP to mRNA
Control of isomerization to the open complex
DNA bending/looping
Cooperativity
Translation can be regulated by ribosomal protein operon |
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Term
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Definition
lacZ encodes -galactosidase (lactose catabolism)
lacY encodes lac permease (lactose transport)
lacA encodes thiogalactoside transacetylase (inactivates toxic thiogalactosides)
Transcription initiation at the lac promoter is regulated by a transcriptional activator (CAP) and a transcriptional repressor (Lac repressor) |
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Definition
Cannot bind to DNA when bound to inducer
Allolactose= inducer
Repressor cannot bind to DNA due to tertiary structure change
Inducer made from lactose by -galactosidase
Made by lacZ
So when lactose is present, lacZ is transcibed and inducer is made
Repressor cannot bind and the lac operon stays on
Binding site found through Dnase-footprinting |
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Term
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Definition
| a point mutation in which a single nucleotide is changed, resulting in a codon that codes for a different amino acid (mutations that change an amino acid to a stop codon are considered nonsense mutations, rather than missense mutations). This can render the resulting protein nonfunctional. |
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Definition
| a point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and in a truncated, incomplete, and usually nonfunctional protein product. It differs from a missense mutation, which is a point mutation where a single nucleotide is changed to cause substitution of a different amino acid. |
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| a genetic mutation caused by indels (insertions or deletions) of a number of nucleotides that is not evenly divisible by three from a DNA sequence. Due to the triplet nature of gene expression by codons, the insertion or deletion can change the reading frame (the grouping of the codons), resulting in a completely different translation from the original. The earlier in the sequence the deletion or insertion occurs, the more altered the protein produced is. |
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| sequence which occurs on eukaryotic mRNA and has the consensus (gcc)gccRccAUGG, where R is a purine (adenine or guanine) three bases upstream of the start codon (AUG), which is followed by another 'G'.[1] The Kozak consensus sequence plays a major role in the initiation of the translation process. |
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Needed for the CAP to bind to DNA
Due to tertiary structure change
cAMP levels decrease with glucose, increase with lactose
Adenylyl cyclase makes cAMP
Activity changes due to the sugar present |
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Recognizes the stop codon hydrolysis of the peptide chain
Prokaryotes have 3, eukaryotes have 1 |
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Definition
Stimulate the release of Class I
Only 1 in Prokaryotes and Eukaryotes |
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Definition
Ribosome can get “stuck”
mRNA is damaged because of bad transcription or degradation
Bad mRNA “stuck” ribosome that cannot be used or forms bad proteins
SsrA helps release the ribosome from the mRNA
Both bad protein and mRNA must be destroyed |
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