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Translation

Translation. Purpose: Translation is the process by which proteins are made Location: On the ribosome. About Proteins. Polypeptide chain Composed of amino acids held together by peptide bonds. Met. Val. Phe. Gly. Tyr. Amino Acids. About Proteins. Polypeptide chain

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Translation

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  1. Translation

  2. Purpose: Translation is the process by which proteins are made • Location: On the ribosome

  3. About Proteins • Polypeptide chain • Composed of amino acids held together by peptide bonds. Met Val Phe Gly Tyr Amino Acids

  4. About Proteins • Polypeptide chain • Composed of amino acids held together by peptide bonds. Met Val Phe Gly Tyr Peptide Bonds

  5. The Genetic Code • The mRNA is read in sets of three nucleotides = CODONS • The code always begins with a “Start” codon = AUG (methionine) • The code ends with one of three “Stop” codons (UAA, UAG, UGA) which do not code for an amino acid • ALL organisms use the same amino acids and the same genetic code

  6. Reading codons:

  7. The Ribosome • Consists of two subunits – a large subunit and a small subunit • The two subunits join together to read the mRNA • Has three binding sites for tRNA – A (1st), P (2nd) and E (3rd)

  8. Translation • Before translation can occur, mRNA must be transcribed from the DNA in the nucleus • The mRNA transcript is then processed • poly-A tail • methylated cap • Introns removed and exon spliced together

  9. Translation - Initiation • Initiation • An initiator tRNA is loaded onto the small ribosome subunit • The small ribosome subunit attaches to the 5’ end of the mRNA • The small ribosome subunit travels along the mRNA looking for a START codon

  10. Translation – Initiation (cont.) - When a START codon is encountered, the large ribosome subunit attaches to the small subunit - Initiation Complex – formed when the two ribosome subunits attach to the mRNA

  11. Translation - Elongation 2. Elongation: -The mRNA molecule moves between the ribosome subunits. • The mRNA is read and anti-condons on tRNA are matched with codons on mRNA • Amino acids are placed in the correct sequence

  12. Translation – Elongation (cont.) • Enzymes catalyze the formation of peptide bonds between the amino acids

  13. Translation - Termination 3. Termination: - When a stop codon is reached (UAA, UAG, UGA) the ribosome ends the translation. • Stop codons do not code for amino acids

  14. Translation – Termination (cont.) Release factors (proteins) bind to the ribosome and trigger enzyme activity that detaches the mRNA and the polypeptide chain from the ribosome http://www.biologie.uni-hamburg.de/b-online/library/biology107/bi107vc/fa99/terry/images/tlterman.gif

  15. The Central Dogma

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