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4.21 Prokaryotic Genetics

This comprehensive overview explores prokaryotic genetics, detailing the defining features of prokaryotes, such as their unicellular nature and lack of membrane-bound organelles. Dive into the evolution of prokaryotes, their classification into two kingdoms, and the study of Escherichia coli as a model organism. Learn about DNA structure, plasmids, and mechanisms through which bacteria acquire new genes, including conjugation, transformation, and transduction. Discover the roles of essential enzymes in DNA replication and the restriction systems that protect bacteria from foreign DNA.

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4.21 Prokaryotic Genetics

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  1. 4.21 Prokaryotic Genetics By Lance Goodridge and Devin Callanan

  2. Defining Prokaryotes • Unicellular organisms • Lacks cell nucleus • Lacks mitochondria + chloroplasts

  3. Defining Prokaryotes 2 • Very small • Live near water • Extremophiles

  4. Evolution of Prokaryotes • Organized into two kingdoms • Very Old • Controversy

  5. Escherichia Coli • The ‘guinea pig’ bacteria • Good for studying

  6. Genomes • Prokaryotes have a genome • DNA = tight loop (shown right)

  7. Plasmids • Also have Plasmids • Additional genes • Can be integrated into bacteria’s DNA (shown right)

  8. OriC • Starts replication process • “Unzips” the DNA • Many AT bases

  9. Helicase • 2 enzymes for DNA replication • Breaks H-bonds • “Supercoils” DNA • Note: The helix of the DNA was omitted for clarity =>

  10. Gyrase • Releases tension • Rejoins strands • Rejoins bonds

  11. DNA Polymerase I • Arthur Kornberg – 1957 • Key to DNA polymerization • Two types

  12. Polymerase and Exonuclease • 5’ to 3’ polymerase • 5’ to 3’ exonuclease • 3’ to 5’ exonuclease

  13. Other DNA Polymerases • Two other polymerases • Pol II • Pol III

  14. Klenow Fragment • 5’ to 3’ exonuclease removed • Labels DNA • Nick translation

  15. 3 Ways Bacteria Acquire New Genes • Mainly reproduce asexually (binary fission shown => NOT an example of gaining new genes) • Three ways to acquire new genes

  16. The F factor (Detailed) • F+: Bacteria w/ F plasmid + pili • F-: Does not have F factor or pili • Hfr: F factor integrated into host's chromosome + pili • F': Hfr w/o F factor + pili

  17. Bacteria Conjugation • F-factor – bacteria grows pili • Forms conjugation tube • If plasmid integrates – Hfr

  18. Transformation • Transfer of exogenous DNA into bacteria • Does not use bacteria or other viruses

  19. Transduction • Infects bacteria with phages • Phage head + assembly shown => • Generalized Trans. • Specialized Trans.

  20. Phage Reproduction • Phages have a lytic cycle => • Breakdown • Relatively quick cycle

  21. Restriction system • Restriction enzymes • Restriction endonuclease • Restriction methylase • Two together = restriction system

  22. Sites Referenced • “Principles of Genetics” Online Textbook • http://www.sciencegateway.org/resources/biologytext/pge/tools.html • http://en.wikipedia.org/wiki/Prokaryote • http://www.biology.ewu.edu/aHerr/Genetics/Bio310/Pages/ch15page/LN13final.pdf

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