BIOL 3451 1st Edition Lecture 9 Outline of Last Lecture I. 5.8 Crossing Over Involves a Physical Exchange between ChromatidsII. 5.9 Exchanges Also Occur between Sister ChromatidsIII. 5.10 Linkage and Mapping Studies Can Be Performed in Haploid OrganismsIV. 6.1 Bacteria Mutate Spontaneously and Grow at an Exponential RateV. 6.2 Genetic Recombination Occurs in BacteriaVI. 6.3 Rec Proteins Are Essential to Bacterial RecombinationVII. 6.4 The F Factor Is an Example of a PlasmidOutline of Current Lecture I. 6.3 Rec Proteins Are Essential to Bacterial RecombinationII. 6.4 The F Factor Is an Example of a PlasmidIII. 6.5 Transformation is Another Process Leading to Genetic Recombination in BacteriaIV. 6.6 Bacteriophages Are Bacterial VirusesV. 6.7 Transduction is Virus-Mediated Bacterial DNA TransferVI. 6.8 Bacteriophages Undergo Intergenic RecombinationVII. 6.9 Intragenic Recombination Occurs in Phage T4VIII. 7.1 Life Cycles Depend on Sexual DifferentiationIX. 7.2 X and Y Chromosomes Were First Linked to Sex Determination Early in the Twentieth CenturyX. 7.3 The Y Chromosome Determines Maleness in HumansXI. 7.4 The Ratio of Males to Females in Humans Is Not 1.0XII. 7.5 Dosage Compensation Prevents Excessive Expression of X-Linked Genes in Humans and Other MammalsCurrent LectureI. 6.3 Rec Proteins Are Essential to Bacterial Recombination- RecA protein: important for recombinant including single-strand displacementi. First one identifiedii. Catalyzes the strand exchange- RecBCD: important for unwinding double-strand DNAi. creates substrate for RecAii. cleave DNA molecule, then back to single strandII. 6.4 The F Factor Is an Example of a PlasmidThese 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.- Plasmids: tend to be circular, but not alwaysi. Multiple copies in cytoplasmii. May contain one or more genesiii. Genes that are useful, but no essential (if essential, then they would be on chromosome)1. Useful for group, but not individual put on plasmid2. Someone survives, and then they repopulate3. Replicate themselves- F factors: confer fertilityi. Not everyone has it, just a few so can continue- R Plasmids: confer antibiotic resistance (seeing this a lot now)- Col plasmids: encode colicins that can kill neighboring bacteriaIII. 6.5 Transformation is Another Process Leading to Genetic Recombination in Bacteria- Transformation: extracellular DNA taken up and stably put in the chromosomei. like conjugation, trying to see if worksii. Figure 6.121. Degrade 1 strand, becomes single strand2. Once integrated, has one host strand, one new strand: called heteroduplex because not perfectly complementary (from different sources)3. Heteroduplex repair: come and fix, and make sure you use the new one- Genes close enough together to be cotransformed, are linkedi. Helps with mappingIV. 6.6 Bacteriophages Are Bacterial Viruses- Bacteriophages: can inject host bacterium by injecting their DNA- Serves as template for progeny: inject, produce progeny within host cell, and then blow up host cell (called lysed) to release progenyi. Figure 6.14- Plaque Assay: number of phages produced following the infection of bacteriai. Continuing serial dilutions of infected bacteria, then pour onto agar platesto count phages; often have to dilute many, many timesii. By counting number of plaques (areas clear of bacteria) on plates, you can determine the number of phages in original culture1. Figure 6.15- Lysogeny happens when: phage DNA integrated into bacterial chromosomei. Replicated along with chromosomeii. Passed on to daughter cells- Bacteria containing prophage are lysogenic and can grow and divide stably until viral production is inducedV. 6.7 Transduction is Virus-Mediated Bacterial DNA Transfer- Bacteriophages can undergo genetic recombination- Infects with operon instead (different than transformation)- This is injected; doesn’t go through membrane like in transformation- Lederberg-Zinder experimenti. Figure 6.161. Something sent DNA across, 2. Accidently sent DNA (transduction)- Generalized Transductioni. Bacterial DNA accidentally packaged instead of phage DNA and transferred to recipient hostii. Results in large number of bacterial genesiii. Can be used in linkage and genetic mapping (like transformation can)- Specialized Transductioni. The phage always inserts in specific spot, misfires, and brings out different bacterial DNA along with phage DNAii. Only a few bacterial genes are transferrediii. Figure 6.17VI. 6.8 Bacteriophages Undergo Intergenic Recombination- Phage mutation often affect plaque morphologyi. Looking at phenotype of phage only1. often affect plaque morphology2. important to understanding genetic phenomena in phagesii. Fig. 6.18 and table 6.1iii. Lysogen or living? Can mutate it…- Mixed Infection: intergenic recombination occurs in bacteriophage (and phage)VII. 6.9 Intragenic Recombination Occurs in Phage T4- Hard to do with peas (with Mendel)- Want to study when genes are really close together?i. Then you put a million upon a million on 1 plate so you can determine if possible.ii. Or determine if they are stuck together - Seymour Benzer’s i. rII locus of pahge T4 allowed him to produce a genetic map of this locusii. they were kept, then sequenced all of them, and found he was correct- Wild-type recombinant phage could be produced from simultaneous infection of E. coli by tow mutanti. 2 cells infected with same and see recombinationii. Multiplicity of infection and at the same timeiii. Frequency of this occurrence if proportional to the distance between the two mutations being studiediv. Figure 6.191. 1 doesn’t work, but 1 is restored and worksv. Figure 6.211. 2 million dead phages for every 1 that works (not possible to do with pea plants really (would need millions of plants), so that’s why want the phenotype of dead so easier to notice the one that works!!)- Some mutants were found to complement each other without intragenic recombinationi. This is complementation: together we can get everything1. Don’t need to do recombination2. Resulted in cistrons: different complementation groups (another term for gene)3. Figure 6.204. This happens 100% of time if both are there, unlike recombinationwhere only happens every 1 in a million5. 2 mutations in same cistron creates no complementation6. 2 mutation s in different cistron= yes