Term
| how many codons are there? |
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Definition
| 4 bases 3 nucleotides=64 codons |
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Term
| in which direction is a protein synthesized |
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Definition
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Term
| in which direction are nucleotides read |
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Definition
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Term
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Definition
do not encode an aa
UGA, UAA, UAG
u go away, u are away, u are gone |
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Term
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Definition
AUG (methionine) only
starts all protein synthesis
DOES code for the amino acid. AUG is the ONLY codon for methionine.
there could be an AUG down stream but it wont start anything |
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Term
| how many codons code for an amino acid |
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Definition
| 63 codons - 3 stop codons = 61 codons |
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Term
| what if there is another stop codon down stream? |
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Definition
| too bad you already stopped at the first one |
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Term
| what are the 4 words that describe the genetic code |
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Definition
| specific (a codon specifies one aa), universial (across most orgnanisms), redundant aka commaless (each aa may have >1 codon), non overlaping (every third base is a codon) |
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Term
| what is different about non coding region codons |
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Definition
| not grouped into triplets |
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Term
| what types of mutations can occur in DNA |
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Definition
| single nucleotide, silent, missense, conservitive, nonsense, insertions, deletions, frameshift, splice site, trinucleotide repeat extension |
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Term
| single nucleotide mutation |
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Definition
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Term
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Definition
| no effect on final protein, codon changes but codes for the same aa |
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Term
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Definition
| different codon leads to a different aa |
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Term
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Definition
| missense mutation but new aa has the same properities as the original |
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Term
| insertion / deletion mutation |
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Definition
adding / subtracting nucleotides from a coding region
can cause a frameshift mutation
if it is a multiple of three added / subtracted and amino acid is completely deleted or added and the frame isnt shifted, no trunkation |
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Term
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Definition
| insertion / deletion mutation that is not a multiple of three. the closer to the begining of the sequence the worse it is. a stop codon is usually introduced pretty soon leading to a trunkated protein |
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Term
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Definition
| codon becomes a stop codon when mutated |
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Term
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Definition
| splice site sequences are specific, changes lead to deletion of nucleotides from the exon, leaving nucleotides from an intron, deleting an exon, can be point mutations |
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Term
| trinucleotide repeat expansion |
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Definition
| sequences of bases, in coding or non coding regions, tend to get expanded by DNA polymerase. if it gets too big it causes problems |
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Term
| what happens if the nucleotide repeat in a coding region is expanded too much |
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Definition
trinucleotide repeat expansion mutation
it expands the protein |
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Term
| what happens if the nucleotide repeat in a non coding region is expanded too much |
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Definition
| if it is a small change it is ok, if it is big it interferes with the translation because the 5' and 3' untranslated regions interact. the protein is normal but less protein is made and a cellular feedback loop methlyates the gene to stop production of the mRNA making the protein |
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Term
| what effect does a missense mutation have on a protein |
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Definition
| decrease in function, variable other effects |
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Term
| what effects does a nonsense mutation have on a protein |
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Definition
| shorter than normal, usually non functional |
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Term
| what effects does a frameshift mutation have on a protein |
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Definition
| usually non functional, shorter than normal |
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Term
| what effect does a large segment deletion mutation have on a protein |
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Definition
| loss of function, shorter than normal or entirly missing |
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Term
| what effect does a splice site mutation have on a protein |
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Definition
| addition or deletion of a few aa to deletion of an entire exon |
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Term
| what effect does a triplet repeat expansion mutation have on a protein |
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Definition
in coding region: cause protein product to be longer than normal and unstable
disease often shows anticipation in pedigree |
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Term
| what mutation is sickle cell anemia? what does it effect? |
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Definition
point mutation
effects betas-globin gene (s for sickle cell effected)
normal code: GAG --> glatamic acid (-)
mutant code: GTG --> valine (neutral) |
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Term
| what mutation is PKU? what does it effect? what is the result? what is a symptom? what is a treatment? |
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Definition
nonsense and frame shift mutation
phenylalanine hydroxylase gene: converts phenylalanine to tyrosine
>400 mutations possible
phenylalanine metabolites accumulate
retardation
oral phenylalanine and tyrosine |
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Term
| what mutation is cystic fibrosis? what does it effect? what is the result? |
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Definition
deletion mutation
70% of the time it is 3 base pairs in the coding region of the cystic fibrosis transfer gene
phenylalanine is missing
protein is functional in the membrane but it does not get put on the membrane right so it does not function |
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Term
| what mutation is alpha or beta-thalasemic? what does it effect? |
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Definition
splice site mutation
deficiency in alpha or beta-globin of Hb |
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Term
| what is the most common single gene disorder in humans |
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Definition
| alpha or beta thalassemia |
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Term
| what mutation is fragile X syndrome? what does it effect? what are some symptoms? what is the result? |
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Definition
trinucleotide repeat in a 5' non coding region
FMR-1 gene
retardation, long face, everted ears, large mandible, macro-orchidism (large testicles)
less protein is made, feedback methlyates the gene and stops its mRNA production
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Term
| what mutation is myotonic dystrophy? what does it effect? what are the symptoms? what is the physological result? |
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Definition
trinucleotide repeat in the 3' non coding region
protein kinase gene effected (signal transduction)
muscles contract but do not relax
shuts off the gene |
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Term
| what is the most common inherited cause of mental retardation |
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Definition
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Term
| what is the most common known cause of autism |
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Definition
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Term
| what is the most common adult muscular dystrophy |
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Definition
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Term
what mutation is huntingtons disease? what does it effect?
when is ir diagnosed? |
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Definition
trinucleotide repeat in the coding region
repeat of glutamine codon causes the huntington protein to be unstable and aggergate
nerve cells die, proressive neuro degeneration
diagnosed between age 30-50 |
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Term
| what happens if there are not enough amino acids to make the protein |
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Definition
| translation will stop at the codon for the missing aa |
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Term
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Definition
| you body cannot make them and you need them in your diet |
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Term
| where is an amino acid attached to a tRNA |
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Definition
| to the CCA 3' attachment site |
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Term
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Definition
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Term
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Definition
| three nucleotide sequence on the tRNA that base pairs with the mRNA |
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Term
| aminoacul tRNA synthetase |
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Definition
| enzymes that attach aa to the corresponding tRNA, each one regognises an aa and all the rRNA that pair to it, 20 kinds in humans, can proofread and edit |
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Term
| explain the reaction where an amino acid is linked to the tRNA |
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Definition
aa carboxyl group is covalently bonded to the hydroxyl on the 3' teminus of the tRNA (ester bond)
pyrophosphate is cleaved to two molecules of inorganic phosphate cleaving two high energy bonds |
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Term
| what happens to RNA subunits just befoe translation |
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Definition
| seperated subunits come together |
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Term
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Definition
| binds incoming aminoacyl tRNA |
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Term
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Definition
| binds peptidyl tRNA that carries the chain of aa that have already been synthesized |
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Term
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Definition
| exit site, contains empty tRNA as it is about to leave the ribosome, only in eukaryotes |
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Term
| what is special about proteins made in ribosomes in the RER |
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Definition
| they are destined for post translation modifications or subcellular compartmentalization |
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Term
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Definition
| accessory proteins involved in stages of synthesis. include initiation, elongation, and termination factors |
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Term
| energy required for translation |
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Definition
charging tRNA: 2 high energy bonds from ATP
binding aminoacyl-tRNA to A site: 1 GTP
movement of the ribosome to the next codon: 1 GTP
total 4 |
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Term
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Definition
| moving ribosome to the next codon |
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Term
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Definition
tRNA can recognise more than one codon for a specific amino acid
the third nucleotide of a codon and the 4th nucleotide of an anticodon can bindin non traditional ways allowing a tRNA to recognise more than one codon |
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Term
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Definition
| prokaryotes have multiple coding regions on the same genes |
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Term
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Definition
| eukaryotes have one coding region per gene leading to one protein |
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Term
| prokaryote translation initiation |
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Definition
| shine-dalgarno sequence. rRNA in small subunit has a complimentary sequence to the shine-dalgarno sequence allowing correct alignment with the subunit to the start codon |
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Term
| eukaryote translation initiation |
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Definition
| small ribosome subunit recognises 5' cap and scans along the ribosome until the first AUG is found, this makes them monocystonic |
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Term
| prokaryotic binding of the initiator |
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Definition
| initiator is bound to a formylated methionine at the p site of the ribosome |
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Term
| eukaryotic binding of the initiator |
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Definition
| initiator tRNA binds to first methionine at the p site of the ribosome |
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Term
| what energy requirements are there for the initiating sequence to bind |
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Definition
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Term
| elongation during translation |
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Definition
| delivery of aminoacyl-tRNA after the initiating sequence is to the a site on the ribosome |
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Term
| what is the energy requirement for each step of an elongation? |
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Definition
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Term
| what does phosphotransferase do? where is it located? how does it get the energy to do its job? |
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Definition
| it forms peptide bonds, it is part of the large subunit, it uses the energy from the charged tRNA |
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Term
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Definition
| uncharged tRNA moves to the e site, prptidyl tRNA moves to the p site, aminoacyl tRNA moves to the a site |
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Term
| termination of translation |
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Definition
| when a stop codon appears in the a site release factors releases the polypeptide from the peptidyl-tRNA and uncharged-tRNA from ribosome, ribosome seperates, requires a GTP |
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Term
| how many release factors are there in parkaryotes |
|
Definition
|
|
Term
| how many release factors are there in eukaryotes |
|
Definition
|
|
Term
|
Definition
aka polyribosome
multiple ribosomes can be on one mRNA to speed things up and protect the mRNA |
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