1. Announcements Ms. Laina Long from the UCLA Bridges Program will give a brief presentation today at 10:40 in this room. She will give you an overview of this paid summer research internship program at UCLA and can answer any questions you may have. Essay exam on Friday. I do want to state that while the genetics portion is focused a problem solving format there could be a definition, result to interpret or genetic concept to briefly explain. The emphasis is on the genetic problems. The next problem will be due on THURSDAY March 13 th instead of Tuesday March 11 th.

2. Ch. 8 Viral Genetic Systems part 2

3. Various viral shapes Influenzya A Ebola Herpes HIV

4. Viruses: highly varied RNA containing or DNA containing Single stranded or Double stranded Linear or circular

5. Bacteriophages & Transduction Transduction: gene transfer from virus to bacterium –Virulent phages lytic –Temperate phages lysogenic

6. Virulent Bacteriophages & Lysis

7. Viral Plaques “clear spaces” This “cloudy:area is living bacteria

9. But: Temperate Phages are Lysogenic Bacteriophages

10. Transduction: Using Phages to map bacterial genes E. coli

11. Generalize Transduction Requires lytic bacteriophages Bacterial chromosome degraded Phage can transfer & recombination bacterial gene to different bacterium Rare event

12. Evidence to support transduction

14. Mechanism for: Generalized Transduction

15. Mechanism of Generalized Transduction (one more time)

16. Evidence to support & calculate frequency of recombination following transduction

17. h - r + X h + r - PhenotypeGenotype Clear and smallh - r + Cloudy and largeh + r - Cloudy and smallh+r+h+r+ Clear and largeh-r-h-r- Progeny Phage produced EXPERIMENT SUPPORTING PHAGE RECOMBINATION

19. Count colonies by phenotypes: corresponds to genotypes Determine parental phenotye Determine recombinant phenotype

20. Specialized Transduction “Targeted transfer of genes: genes must be located at specific site on bacterial genome! Location, location, location!

21. Specialized Transduction Gene transfer from phage to bacterium Site specific transfer Requires lysogenic bacteriophages Lambda phage one of the best studied

23. a. Movement of the prophage

24. b. Another possible movement of prophage

25. Now what could happen. Leads to unstable transductant Leads to stable transductant

26. Unstable Transductant

28. Fine Structure Analysis of Bacteriophage genes Early studies on the structure of a “gene” go beyond recombination experiments Mutations were studied in phage Are mutations within the same gene or affecting different genes? Transduction is used to answer these questions. Let’s now look how these studies taught us some key facts about genes.

29. Okay, this sounds familiar

30. Yes, recombination could be observed with these mutants.

31. Let’s take this one step further Complementation experiments using transduction The question is: where do these mutations exist? –Within the same gene or on different genes?

36. Genes may overlap in the viral and prokaryotic genomes!