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Topic 7 Cont’d

Topic 7 Cont’d. Transcription and Translation. Transcription Basics. DNA vs. RNA. Transcription Basics cont’d. Directionality: read 3’-5’; made 5’-3’ Promoter & TATA boxes Nucleoside triphosphates Contains the sense strand and antisense strand

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Topic 7 Cont’d

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  1. Topic 7 Cont’d Transcription and Translation

  2. Transcription Basics • DNA vs. RNA

  3. Transcription Basics cont’d • Directionality: read 3’-5’; made 5’-3’ • Promoter & TATA boxes • Nucleoside triphosphates • Contains the sense strand and antisense strand • Sense strand = always 5’-3’ and is the same as the mRNA that is produced except T for U • Antisense strand = always 3’-5’ and is the strand that forms the template and is transcribed.

  4. Animation sites • http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf • http://vcell.ndsu.nodak.edu/animations/transcription/first.htm

  5. Translation The process of polypeptide/protein production using mRNA as a guide Requires: mRNA transcript tRNA tRNA activating enzymes ribosomes genetic code…..

  6. The Genetic COde

  7. The Genetic Code cont’d • It’s a triplet code (codon) = 3 bases code for 1 amino acid • There are 64 different codons • Duplication = degeneracy = possible for 2 or more codons to code for the same amino acid • Code is essential universal (find me 2 exceptions by next class for 1 point e.c. each)

  8. Amino Acids

  9. tRNA • All tRNAs have base-paired ds sections that become loops • Triplet bases complementary to mRNA codons…called anticodons • A 3’-5’ CCA terminal end for amino acid attachment • The above permit 3 distinct binding attachment of the tRNA to the ribosome

  10. tRNA cont’d

  11. tRNA a S = F example • The base sequence of tRNa molecules vary = some variable features in its structure • An extra small loop is sometimes present • The bp sections are sometimes helical • Results in: • A distinctive 3-d shape • Distinctive chemical properties • ALLOWS THE CORRECT AA TO BE ATTACHED TO THE 3’ END BY A tRNA ACTIVATING ENZYME (aminoacyl-tRNA sythetase) • There are 20 different tRNA activating enzymes – one for each of the 20 diff. AA

  12. Ribosome Basics • Composed of protein and rRNA • Consist of 2 subunits (small and large) • Possess 3 binding sites for tRNA (2 tRNAs can bind at the same time) • Possess a binding site for mRNA • Free vs. Bound (RER) • 80S in Euks vs. 70S in Proks & Euk. organelles

  13. Ribosome (2 site version)

  14. Translation Step 1 - Initiation

  15. Polysomes & Movie Time • http://vcell.ndsu.nodak.edu/animations/translation/movie.htm

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