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Eukaryote - Coggle Diagram
Eukaryote
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Translation
Ribosomes
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Eukaryotes
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60S is 28S, 5.8S and 5S rRNA and 40S is 18S rRNA
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contain exit, peptidyl-tRNA and aminoacyl-tRNA site
tRNA
structure
consists of acceptor arm, D arm, anticodon arm, variable loop (sometimes not there), and TC arm
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Initiator tRNA
first codon is AUG for methionine, and its tRNA is different for other mets
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bacteria use Met-tRNAfmet because their first met is N-formylmethionine (formyl group or whole met is often removed)
Process
Initiation
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binding
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Eukaryotes- subunits, IFs and Met-tRNAimet find 5' cap and find start codon via Kozak sequence and the polyA tail assists small subunit
Elongation
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EF-2 and GTP arrive and deacylated tRNA, EF-2 and GDP detach then amino acid moves out the ribosome
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Termination
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when it reaches the stop codon there is no amino acid to go into the A site and release factor occupies the place
RF cannot form a peptide bond, RF1 recognises UAG,UAA; RF2 recognises UGA, UAA and RF3 releases the polypeptide
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Degeneracy
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it is because the pairing at the third base can mismatch, since the third base is not exactly aligned due to curved nature of tRNA shape
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Discovery
Crick
Observed FCO mutant bacteriophage T4, guessing it was a single base addition
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Nirenberg
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used polynucleotide phosphorylase to make RNA of single base repeats and added all 20 amino acids to each tube and radioactively labelled 1 amino acid
if protein is radioactive then the mRNA sequence transcribes for that amino acid (this could only be done for 4 homopolymers)
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Nirenberg and Leder
produce very short mRNA with known codons, added to ribosome and tRNA mixture
any tRNA with an unmatching anticodon is left and only one that does match binds and the amino acid is bound to ribosome
the unbound tRNAs are filtered and ribosomes remain on filter, and record radioactivity
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Chromatin
Histone
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5 main types- H1, H2A, H2B, H3 an dH4
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