BIOL 3451 1st Edition Lecture 8 Outline of Last Lecture I. 4.13 Genetic Background and the Environment May Alter Phenotypic ExpressionII. 5.1 Genes Linked on the Same Chromosome Segregate TogetherIII. 5.2 Crossing Over Serves as the Basis of Determining the Distance between Genes in Chromosome MappingIV. 5.3 Determining the Gene Sequence during Mapping Requires the Analysis of Multiple CrossoversV. 5.4 As the Distance between Two Genes Increases, Mapping Estimates Become More InaccurateVI. 5.5 Drosophila Genes Have Been Extensively MappedVII. 5.6 Lod Score Analysis and Somatic Cell Hybridization Were Historically Important in Creating Human Chromosome MapsVIII. 5.7 Chromosome Mapping is Now Possible Using DNA Markers and Annotated ComputerDatabasesOutline of Current 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 PlasmidCurrent LectureI. 5.8 Crossing Over Involves a Physical Exchange between Chromatids- Cytological markers used in maize to show that crossing over involves physical exchange of chromosome regionsi. Figure 5.15II. 5.9 Exchanges Also Occur between Sister Chromatids- Sister chromatid exchanges (SCEs)i. Happens during mitosis ii. Figure 5.16These 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.iii. Agents that induce chromosome damage increase frequency of sister chromatid exchange1. Broken, so had to fix itIII. 5.10 Linkage and Mapping Studies Can Be Performed in Haploid Organisms- Eukaryotes that are haploid can mate to form diploid (think yeast)i. Zygote undergoes meiosis to get haploidii. Still do linkage mapping here- Neurosporai. Tetrad (haploid products) is retained in a saclike structure called ascusii. These haploids do mitosis to produce 8 haploid ascosporesiii. Each pair represents a DNA molecule, then the splitiv. 8 ascospores are ordered within the ascus according to the sequence of their formation allowing ordered tetrad analysis 1. Figure 5.18a. Found heterozygosity at the DNA levelb. Didn’t always get 4:4- Ordered tetrad analysisi. Used to 1. determine when crossing over occurred based on the expected patterns of first-division and second-division segregations2. determine if recombination events are reciprocal so you can map the centromereii. Figure 5.19iii. Mapping the centromere: Used to determine the map distance between gene and centromeres- Unordered tetrad analysis also usedi. Determine whether two genes are linked on same chromosomeii. If so, can map distanceiii. Only downside, is you don’t have the orderiv. Figure 5.20 and 5.21- 3 categories of tetrad are produced by tetrad analysis in Chlamydomonasi. Parental ditypes (P)ii. Nonparental ditypes (NP)iii. Teratypes (T)iv. Table 5.1IV. 6.1 Bacteria Mutate Spontaneously and Grow at an Exponential Rate- Why study bacteria?i. Easy to culture, don’t take up much space so can do in large numbersii. More simple than eukaryotes (easier to determine processes then look at humans)- Adaptation hypothesisi. Interaction of bacteriophage and bacterium is essential to the bacterium’sacquisition of immunity to the phageii. Exposure to the phage “induces” resistance in the bacteriaiii. Lysogens (makes resistant to being killed by relatives) and also make new phages if needediv. Phages need a host to survive- Spontaneous mutation that occurs in the presence or absence of phage is considered the primary source of genetic variation in bacteriai. Phage is better than bacteria in the sense of producing numbers - Selection: where only the mutant of interest grows well, where the wild type does not (makes is easier-the one where the most will result, make sure they die so easier to count)- Prototroph: can synthesize all essential organic compounds and therefore can be grow on minimal medium- Auxotroph: (through mutation) lost the ability to synthesize one or more essential compounds; must be provided with them in the medium if it is to grow- Bacteria have three phasesi. Lag pahseii. Log phase (growing)iii. Stationary phase (live in sewer of own making, less food, environment becomes toxic or nutrients are exhausted so will stop dividing. Then, eventually die.)iv. Figure 6.1V. 6.2 Genetic Recombination Occurs in Bacteria- Conjugation: sex in bacteriai. Genetic info transferred from one to anotherii. Can recombine with the second bacterium’s and create new (that’s why not good because you can’t always identify it)- Figure 6.5i. F+ cells are DNA donors and F- cells are recipientsii. F+ cells have fertility factor (F factor) that confers ability to donate DNA in conjugationiii. Recipient cells are converted to F+1. From evolutionary standpoint, good because if they come across something that will be good for them, they will pick it up- E. Coli may or may not contain the F factor- When F factor is present, the cell is able to form a sex pilus and serve as a donor of genetic info- During conjugation, a copy of the F factor is transferred from the F+ cell to the F- recipient, converting the recipient to the F+ statei. Have to get whole plasmid to become F+- Hfr (high-frequency recombination) strain has the F factor integratedi. Hfr strain can donate genetic info to F- cell, but it usually never becomes F+1. Why? F plasmid becomes a part of the plasmid (higher rate of recombination here)- Interrupted matings: demonstrated that specific genes in an Hfr strain are transferred and recombined sooner than others i. Figure 6.61. The longer you go, you begin making your way around the chromosomeii. Chromosome of an Hfr strain is transferred linearly iii. Gene order and distance between genes can be predicted in time mapping1. figure 6.7- Gene transfer led to discovery of E. coli chromosome being circular- F factor can go in and come out, not usually perfect incision because it will pick up genes around it (Figure 6.11)i. Merozygote is produced (partially diploid)1. Figure 6.10VI. 6.3 Rec Proteins Are Essential to Bacterial Recombination- Rec A (nonitalics is the protein, if italicized, then it