BIOL 240 1st Edition Lecture 16Outline of Last Lecture I. Bacterial GenomeII. Genotypic SymbolsIII. Bacterial DNA ExchangeOutline of Current Lecture I. Hfr StrainsII. DNA TransferIII. TransformationIV. Bacteriophage T4V. TransductionCurrent LectureI. High Frequency of Recombination (Hfr) Strains- What are they?o An Hfr strain is created when the F factor (plasmid) integrates into thebacterial genome of the recipient cell.- Once the F plasmid is integrated, it can transfer bacterial chromosomes through crossing over, or recombination.II. DNA Transfer- DNA transferred as a single strand- Donor chromosome segments that are not integrated are diluted or degraded. Bacterial recombination is nonreciprocal.- Single crossovers do not work…the product is a linear DNA molecule that is degraded.III. Transformation- Fragment of chromosome of a dead bacterium- Same or different species- Only some bacteria are able- Extracellular DNA binds to a cell’s receptor site. The DNA enters and the stands separate. One strand of DNA is degraded and the other pairs homologously with the host cell DNA. The DNA recombines with the host These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.chromosome, replacing its homologous region. After one round of cell division, a transformed and a non-transformed cell are produced.IV. Life Cycle of Bacteriophage T4- what is it?o viruso head packages with DNA1. Phage is adsorbed to bacterial host cell.2. Phage DNA is injected and the host DNA is degraded.3. Phage DNA is replicated and proteirn components are synthesized.4. Mature phages are assembled.5. Host cell is lysed and phages are released.V. Transduction- Another form of bacterial recombination- Experiment: two opposite strains are placed in a U-tube with a filter. When plated on minimal medium, one strain shows no growth and the other does. This showed that recombination did not occur through conjugation (because with conjugation there must be cell to cell contact). Addition of DNase, whichdestroys naked DNA, did not affect the results, so recombination did not occur through transformation either.- Hypothesis—bacteriophage were acting as vectors to transfer bacterial genes…this was called “transduction”- Plaques—clear area in which all bacteria have been lysed by phages. Phage infect bacteria, kill them , and infect their neighbors, spreading until a clear area is produced.o r- causes rapid lysis and yields large plaqueso r+ causes slow lysis and yields small plaqueso h- forms clear plaques (infect both bacterial hosts)o h+ form cloudy plaques (infect only one of the
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