BIOL 3451 1st Edition Lecture 10 Outline of Last 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 MammalsOutline of Current Lecture I. 7.5 Dosage Compensation Prevents Excessive Expression of X-linked Genes in Humans and Other MammalsII. 7.6 The Ratio of X Chromosomes to Sets of Autosomes Determines Sex in DrosophilaIII. 7.7 Temperature Variation Controls Sex Determination in ReptilesIV. 8.1 Specific Terminology Describes Variations in Chromosome NumberV. 8.2 Monosomy and Trisomy Result in a Variety of Phenotypic Effects VI. 8.3 Polyploidy, in Which More Than Two Haploid Sets of Chromosomes Are Present, Is Prevalent in PlantsVII. 8.4 Variation Occurs in the Internal Composition and Arrangement of ChromosomesVIII. 8.5 A Deletion is a Missing Region of a ChromosomeCurrent LectureI. 7.5 Dosage Compensation Prevents Excessive Expression of X-linked Genes in Humans and Other Mammals- Barr Body: inactivated X chromosome (why females don’t usually exhibit X-linked disorders) Can still have an impact even if inactivatedThese 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.- Lyon Hypothesis: one gets inactivated (random), and happens at multicellular stageso is more of a mosaic (take from different areas/patches)  Calico cats and fur color/patterns- Mechanism of inactivation Xic: active on the inactive X, just one of them Creates XIST (X-inactive specific transcript) geneII. 7.6 The Ratio of X Chromosomes to Sets of Autosomes Determines Sex in Drosophila- Y does not determine sex (like in humans) Sex determined by X ratio Male x chromosome is upregulated (which is fine because most genes are notworking at full capacity in normal conditions anyway) Figure 7.12 (2A means normal diploid autosomes)III. 7.7 Temperature Variation Controls Sex Determination in Reptiles- Temperature change controls sex determination in reptiles Depends on incubation temperature of eggs- 3 different patterns of temperature sex determination in reptiles (figure 7.15) Most reptile species use: ZZ/ZW or XX/XY (mammals and humans came from reptiles so notice similarities)IV. 8.1 Specific Terminology Describes Variations in Chromosome Number- Diploids normally have exactly 2 haploid chromosome sets, but some variation Change in total number Deletion/duplication of genes, missing/changing parts of chromosome Rearranging material on chromosome Called Chromosome mutations/aberrations (different than gene mutations)- Aneuploidy Gaining or losing one or more chromosomes (doesn’t have to be a full set)1. Like XXY Not good (mostly dead, if not, then organism is most often sterile) Arises from nondisjunction where chromosomes don’t separate correctly  Usually causes abnormal phenotype (imbalance of amount of gene products-gene regulators, etc) (Figure 8.1) Table 8.11. Most changes in autosomes do not result in births, they die2. Euploidy: (for humans, is diploid-normal)3. Allopolyploidy: doesn’t work well in mammals4. Allotetraploidy: 2 diploid genomes (found in plants)a. Go through S phase and not divide…turns out that works 5. Allohexaploidy: worked once, now try again V. 8.2 Monosomy and Trisomy Result in a Variety of Phenotypic Effects- Monosomy In humans, this phenotype is dead (except in X and Y chromosomes, unless male doesn’t get X chromosome, then he dies) Not tolerated in autosomes in humans and other animals- Trisomy Often lethal, except for a few chromosomes which are all small (21,22,)1. Why? The bigger you get, the more ratios that are messed up, therefore more things don’t work 3 copies of one chromosome are present, makes meiosis irregular because synapse regions vary Get a trivalent instead of bivalent, also can get a univalent Very unstable Down Syndrome (trisomy of maternal chromosome 21)1. 12-14 characteristics, but most only have about half of these2. Karyotype for this, PCR doesn’t pick it up3. Increases incidence with increasing maternal age4. Sometimes runs in families (called familial down syndrome)a. Involves a translocation of chromosome of 21b. Not as severe because only involves a part of 21c. More common Often spontaneously aborted (about 5%) because body knows it won’t make it; where as, monosomies are not- Genetic counseling is recommended for women becoming pregnant later in life Why? Because now we can screen for all different types of genetic disorders Amniocentesis/chorionic villus sampling (CVS): diagnostic testing- Patau syndrome (trisomy 13)- Edwards syndrome (trisomy 18) Both very bad (figure 8.5)VI. 8.3 Polyploidy, in Which More Than Two Haploid Sets of Chromosomes Are Present, Is Prevalent in Plants- Based on number of chromosomes found: Triploid: 3n Tetraploid: 4n Pentaploid: 5n- Polyploidy in plants originates by: Adding one or more sets of chromosomes to the same haploid (same species)= autopolyploidy1. Autotriploids: arise in different ways2. Autotetraploids more prevalent in natural population because produce normal gametes Interspecific mating that results in a combination of chromosome sets from different species=allopolyploidy1. Allotetraploid: results from hybridization of two closely related species2. Amphidiploid: sterile hybrid doubles chromosomes, fertile amphidiploid produceda. produced by somatic cell hybridization, then take cells and do hybridization=fuse to make different cells3. Figure 8.8- Endopolyploidy: certain cells in body aren’t diploid, but haploid or polyploidy In polyploidy cells, replication and segregation occur without nuclear divisionVII. 8.4 Variation Occurs in the Internal