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  • Transcript

    • 1. Microbial genetics Bios 10115 February 18, 2010 Additional reading from your book is suggested-Ch 4 pp 61-80
    • 2. “Central Dogma” (DNARNAProtein)  Genetic information of all cells is in DNA  DNA is duplicated during the process of DNA Replication  Transfer of genetic information to RNA occurs during Transcription  RNA is converted to protein during translation
    • 3. DNA  4 nucleotides  GATC  Nucleotides consist of pentose sugar (5’ and 3’ positions), phosphate and backbone
    • 4.  Double stranded-held together by hydrogen bonding-base pairs  A-T (2 H bonds)  G-C (3 H bonds)  Chromosome  Threadlike Double helix of DNA  Prokaryotes-Circular (most)  Eukaryotes- linear  Virus-circular or linear
    • 5. Double Helix – ________ strands
    • 6. DNA higher order structure E. coli has 1.5mm of DNA
    • 7. Figure 10.1a: An electron micrograph of an E. coli cell immediately after disruption. The tangled mass is the organism’s DNA. © H. Potter-D. Dressler/Visuals Unlimited.
    • 8. Eukaryotic DNA higher order structure “beads on a string”
    • 9. Information transfer  Replication  DNA makes new (is the template for) DNA  Transcription  DNA is the template for RNA  Translation  RNA is the template for proteins A template is a pattern that is faithfully copied
    • 10. DNA replication  New strand is made as complement of template strand  Each daughter double helix has one parental strand and one newly synthesized strand  DNA replication always occurs 5’-3’  5’ Phosphate attaches to 3’ hydroxyl using DNA Polymerase
    • 11. The DNA replication fork (E. coli) Leading and lagging strands DNA polymerases can only move in one direction
    • 12. http://www.dnai.org/a/index.html (animations of replication, E. Coli replicates 1000 bases per second
    • 13. Replication of circular DNA Also see fig 10.2 of your book
    • 14. RNA  Ribose instead of deoxyribose  Uracil instead of Thymine  Single Stranded (except some viruses)  Messenger (mRNA)  Transfer (tRNA) All transcribed from DNA  Ribosomal (rRNA)
    • 15. Transcription  An RNA copy of DNA must be made first before proteins can be synthesized  Transcription requires the enzyme RNA Polymerase
    • 16. Translation  Translation is the process of synthesizing protein from RNA  Three types of RNA involved
    • 17. Figure 4.8: The translation process
    • 18. The Genetic Code  Codon-set of 3 nucleotides that encodes an amino acid  Amino acid-building block of protein  Start Codon - AUG- methionine  Stop codon- terminator- UAA, UAG, UGA
    • 19. Figure 4.9: A summary view of protein synthesis
    • 20. Open reading frames
    • 21. Mutations- changes in DNA Genotype -genetic info  Always changed by a mutation Phenotype -outward appearance  May not change with mutation Point mutations  A single nucleotide has been changed  A single codon is changed  May or may not change amino acid sequence (silent mutation)
    • 22. Mutations (cont.) Frameshift mutations  A deletion or insertion of one or more bases  Changes ORF  Usually change phenotype
    • 23. Mutations (cont.)  Spontaneous mutations  Occur in the absence of any known agent  Arise during DNA replication  Bacterial genes have a relatively high spontaneous generation rate  Induced mutations  Caused by mutagens
    • 24. Mutagens  Chemical  Many different effects at molecular level  Base analogs  Alkylating agents  Deaminating agents  Acridine derivatives  Radiation  Thymine dimers
    • 25. Plasmids Small, circular extra-chromosomal DNA Do not carry essential genes May carry helpful genes Replicate independently of chromosome Over 300 naturally occurring plasmids have been isolated from E. coli
    • 26. Gene transfer  Vertical gene transfer-parents to offspring  Lateral (or horizontal) gene transfer-passing of genes within a generation  Transformation  Transduction (virus mediated)  Conjugation http://www.microbelibrary.org/microbelibrary/files/ccImages/Articleimages/ Mondomedia/4hirez.mov
    • 27. Also see figs 10.5-10.9 in your book
    • 28. Figure 10.9a: Bacterial transformation Free DNA taken up by cell © National Library of Medicine
    • 29. Genetic exchange-Transformation Streptococcus pneumoniae (pneumococcus) +/- capsule 1928-pneumococcus expt (Griffith) 1944-transforming compound is DNA 1953-structure of DNA Also fig 4.2 of your book
    • 30. Transduction  Transfer of DNA by a _____________
    • 31. Conjugation: _______ transfer of plasmids  Ability is encoded by _________  Donor cell produces ____  New population can gain plasmid very quickly
    • 32. Manipulation of DNA and Genetic engineering
    • 33. Tools to manipulate DNA  ___________________ Sequences usually palindromic (enzymes)  Derived from _______  Protect bacteria from _______________  Recognize specific small sequences of DNA and ___ _________ leaving “sticky” (staggered) or “blunt” (straight) ends  Bacteria’s own DNA _________ by methylation
    • 34. Figure 10.10a: A restriction enzyme cuts through two strands of a DNA molecule to produce two fragments.
    • 35. Figure 10.10b: The recognition sites of several restriction enzymes
    • 36. Recombinant DNA technology  Recombinant DNA  DNA from _________  Transgenic or recombinant organism  Organism derived from recombined DNA  _______  Self replicating DNA (plasmid)
    • 37. Figure 10.11A-B: Construction of a recombinant DNA molecule
    • 38. Figure 10.11C-E: Construction of a recombinant DNA molecule
    • 39. Figure 10.12A-C: Developing new products using genetic engineering
    • 40. Figure 10.12D-G: Developing new products using genetic engineering