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Decoding Translation: From DNA to Protein Synthesis

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Understand the process of translation, from ribosomes to mRNA, amino acid pairing, and the genetic code to protein synthesis. Learn about initiation, elongation, termination, and post-translational modifications of proteins.

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Decoding Translation: From DNA to Protein Synthesis

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  1. Announcements • Homework for Chapter 7 Part 2 due Wednesday • Remember, lab 4 is Thursday • No online quiz because it was due days ago • Check your email at least 3 times a day!

  2. Chapter 7, Part 2:The Blueprint of Life, from DNA to Protein

  3. The Players In Translation Ribosome mRNA • What do they do? • String amino acids together, recognize where translation begins • How does it move along mRNA? • 5’ to 3’ tRNA • Pairs with? • Codons • How it pairs? • Complementary • Carries what? • Appropriate amino acid • Made from what? • DNA • Carries what? • Genetic code • How? • 3 nucleotides make up an amino acid

  4. How Is Translation Initiated? • Translation starts BEFORE mRNA transcription is finished! • How does the ribosome know where to bind? • There’s a sequence/binding site for that! Ribosome-binding site • When/where does it start translating after it bind to the site? • The first start codon: AUG • Remember it is going in the 5’ to 3’ direction!

  5. Let’s Review…The Genetic Code

  6. Why Is The Genetic Code Redundant? • Remember a codon is a triplet of the 4 possible nucleotides • A U G C • So, how many combinations can you have? • 43=64 • How many amino acids are there? • 20 • So, how do you have 64 codons for 20 amino acids? • Because several different combinations code for the same amino acid • Example: UUU and UUC both code for Phenylalanine

  7. More About the Start Codon… 5’ • Can it be a start codon without a ribosome binding site? • No • Why? • No ribosome binding site=no ribosome • So what is it? • Just a methionine then • Question: How can we make this AUG be a start codon? • Add Ribosome binding site. • Where? • 5’ end • **Only an AUG that is a start codon in bacteria is a chemically altered form of methionine called N-formylmethionine (f-Met)** GCACCAUG 3’

  8. INITIATION

  9. Elongation

  10. Termination

  11. Activity Let’s work together to translate the mRNA on the board Each of you are a tRNA! Do you have a codon or anticodon? Anticodon

  12. Once A Protein Is Made…Now What?Post-Translational Modifications • Proteins need to be folded into 3D structures to be functional • How is this accomplished? Chaperones • Transported to their respective “compartments” • How? Signal sequence • Phosphorylation

  13. Question Now that we know how a bacteria goes from a gene encoded in the DNA to actually expressing it, do you think bacteria want to make all gene products (i.e. proteins) all the time? Why or why not?

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