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Translation

Translation. or "Protein Assembly". DNA -> RNA -> amino acids -> Proteins. Prokaryotic cells do not contain a nucleus so both transcription and translation occur in the cytoplasm. Messenger RNA is converted to amino acids by ribosomes. Virtual cell: Translation. Key Players. mRNA.

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Translation

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  1. Translation or "Protein Assembly"

  2. DNA -> RNA -> amino acids -> Proteins Prokaryotic cells do not contain a nucleus so both transcription and translation occur in the cytoplasm Messenger RNA is converted to amino acids by ribosomes Virtual cell: Translation

  3. Key Players mRNA Copy of the DNA template strand which is translated into amino acids Ribosomal Subunits ·A protein made of two subunits:(one large and one small) and rRNA ·the 2 subunits bind together with mRNA to produce the new protein made up of a polypeptide chain ·The ribosome contains two sites: - A site (acceptor) - P site (peptide) mRNA binding site

  4. Key Players tRNA · Delivers amino acids to ribosome ·About 80 nucleotides long ·Folds back on itself to create a 3D structure (cloverleaf)‏ ·Each tRNA carries its own amino acid based on the anticodon ·Therefore, at least 20 different types of tRNA are needed Release Factor There is no tRNA for the stop codon but a release factor is used in its place to end translation of the peptide.

  5. The Genetic Code codon: sequence of three bases inDNAor complementary mRNA that serves as a code for a particular amino acid start codon: specific codon (AUG) that signals to the ribosome that the translation commences at that point stop codons: specific codons that signal the end of translation to a Ribosome (UAA, UAG, UGA)

  6. Translation (in cytoplasm) ·Initiation: -ribosome binds to mRNA at 5’ end (AUG – start codon) -reads mRNA and recruits tRNA to get coded amino acid -aminoacyl-tRNA brings amino acids for building the protein -AUG (Methionine) brought by tRNA to the ribosome P site anticodon start codon

  7. Elongation: - the next tRNA brings the new amino acid to A site (Ala), · - the old amino acid from the P site (Met) joins to the new A site amino acid (Ala) forming a peptide bond. - ribosome slides down one codon, tRNA (Ala) slides from A site to P site, and the tRNA from P site (Met) moves off the ribosome -The next tRNA brings in a new amino acids to the A site (Ile) and the process continues

  8. Termination: 1) Ribosome reaches a stop codon (UAA, UAG, UGA) and stalls because no tRNAanticodon to stop codon. 2) A Release Factor protein recognizes the stall, and releases the polypeptide chain from ribosome 3)the two subunits of the ribosome fall off of the mRNA transcript Release Factor Protein

  9. Often many of the same proteins are needed. The same mRNA can be used by different ribosomes attaching to the mRNA at different times. POLYRIBOSOME

  10. Transcription Relay Race In groups of 5 your will be competing against the other groups to see who are the fasted tRNAs. Each group will be given a piece of paper with their mRNA sequence on it and both a large and small ribosomal subunit. Scattered around the class are cue cards with the tRNAanticodon and amino acid on them. One person at a time will go look for the anticodon needed, bring it back and place it in the correct A or P site. This will act like a relay race and now the next person on the team must go find the appropriate anticodon and bring it back to their ribosome. Once you reach the stop codon make sure you find the Release Factor protein to win the race. The first group to bring their polypeptide to the teacher will WIN!!!! Rules: NO running, physical contact, hiding cards or bringing back more than one card at a time.

  11. Homework Link DNA to protein review McGrawHill text Read 6.3 pg 257-261 Answer #13-18pg 260 Next up: mutations pg 262-265 #19-24pg 265 Nelson text Read pg. 250-254 Answer Questions 1-4, 6, 9

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