1 / 25

Bio 178 Lecture 30

Bio 178 Lecture 30. Gene Expression. http://ccgb.umn.edu/~mwd/cell_www/chapter2/ribosome.html. Reading. Chapters 15 & 20 (P 410-411). ?. Quiz Material. Questions on P 318 & 432 Chapters 15 & 20 Quizzes on Text Website (www.mhhe.com/raven7). Gene Expression

prisca
Download Presentation

Bio 178 Lecture 30

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bio 178 Lecture 30 Gene Expression http://ccgb.umn.edu/~mwd/cell_www/chapter2/ribosome.html

  2. Reading • Chapters 15 & 20 (P 410-411) ? Quiz Material • Questions on P 318 & 432 • Chapters 15 & 20 Quizzes on Text Website (www.mhhe.com/raven7)

  3. Gene Expression • Transcription (Cntd.) • Translation • Mutation • Somatic and Germ-Line • Types of Mutation Outline

  4. Transcription Initiation RNA pol has no proofreading ability - why is this not a problem?

  5. Transcription (Cntd.) 4. Termination At the end of the gene “stop” sequences cause transcription to stop, the RNA-DNA hybrid to dissociate, & the DNA in the transcription bubble to rewind. Example of a Stop Signal: Series of GC base pairs, followed by series of AT base pairs  GC hairpin followed by a polyU sequence. Hairpin causes RNA pol to pause, & the pairing of U with A is weak  Dissociation.

  6. GC Hairpin

  7. Transcription in Eukaryotes Some of the important differences from prokaryotes include: • Transcription Factors Additional proteins that are required for transcription. • RNA Polymerases 3 different RNA polymerases with different functions. • Promoters The different RNA polymerases use different promoters. The RNA pol II promoter (for mRNAs) has a core sequence called a TATA box.

  8. Initiation of Transcription in Eukaryotes

  9. Transcription in Eukaryotes (Cntd.) • Posttranscriptional Modifications 1. 5 Cap GTP is added to the 5 end of the transcript. A methyl group is then added to the G of the GTP. Function - Stability & initiation of translation. 2. 3  Poly-A Tail The transcript is cleaved downstream of a specific site. Many A’s are added to the 3 end. Function - Stability.

  10. Posttranscriptional Modifications

  11. Eukaryotic Posttranscriptional Modifications (Cntd.) 3. Intron Removal • Introns Region of the DNA that is transcribed but does not code for protein. Removed from the transcript prior to translation. • Exons Coding regions of DNA.

  12. Posttranscriptional Modification

  13. Translation

  14. Prokaryotic Translation - Initiation

  15. Translation (Prokaryotes) 1. Leader sequence of mRNA binds with rRNA of the small ribosomal subunit. 2. The first codon is AUG. The complementary anticodon on tRNA binds to the codon. This tRNA carries the amino acid fMet. 3. The large ribosomal subunit binds. tRNAfMet is in the P site.

  16. Prokaryotic Translation - Elongation & Translocation

  17. Translation (Cntd.) 4. tRNA with the appropriate anticodon binds to the codon in the A site. 5. fmet is released from its tRNA and a peptide bond is formed between it and the second amino acid. 6. Ribosome moves 3 nts 53. Initial tRNA now in E site, from where it leaves. 7. Appropriate tRNA binds to A site and the process continues until a stop codon is reached.

  18. Translation - Termination

  19. Translation (Cntd.) 8. When a stop codon is reached it binds a release factor. 9. The bond between the protein and the tRNA in the P site is broken and the protein released. Translation in Eukaryotes Principle differences from prokaryotes: First amino acid is met. 5 cap binds to rRNA.

  20. Secreted Proteins http://cellbio.utmb.edu/cellbio/ribosome.htm

  21. Summary of Gene Expression

  22. Question Example For the DNA sequence (on the template strand): 3-ACTACTGAGTAGCCCAGCTAACTCCTGTT-5  Give the mRNA sequence, and using the genetic code, the amino acid sequence of the corresponding protein.

  23. Translation McGraw-Hill Video

  24. Mutation

  25. Mutation Changes in the hereditary message of an organism. • Somatic Mutations Not inherited, but can have a profound effect on the individual, eg. Cancer. • Germ-Line Mutations Inherited. Importance Starting point for evolution - mutation produces new alleles and recombination shuffles them. Do all Germ Line Mutations Increase Genetic Fitness? No - May reduce, maintain, or increase progeny number.

More Related