BIOL 310 1st Edition Lecture 7 Outline of Previous Lecture- MendelismI. Chromosome Types & TranslocationII. Mitosis and Meiosis are part of the cell cyclea. Chromosome structureOutline of Current Lecture:I. Purposes of MeiosisII. Meiosis Ia. Prophase, metaphase, anaphase, telophase ; whats up with all this DNA?III. Meiosis IIa. What is different between Meiosis, Mitosis and Meiosis II?IV. Sex Determinationa. X-Chromosome BasedV. Types of sex determinationa. Environmentalb. X/Y VI. What happens when things go wrong? a. Turner Syndromb. Klinefelter SyndromI. Purposes of meiosis:1. To create genetic diversity via crossing over & independent assortment2. Halves the amount of genetic informationII. Meiosis IMeiosis is very similar to two rounds of mitosis:In Interphase: chromosomes get replicatedMeiosis 1: halving of chromosomes (Reduction Division)Meiosis 2: Each sister chromosome separates into singular chromosomes (equational division)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.Differences include:Meiosis has 1 round of replication and 2 of divisionMitosis has 1 round of replication and 1 of divisionProphase I- homologs pair up; diversity created here because recombination occurs Leptotene- Break in DNA begins pairing; chromosomes are condensing into short spaghetti; recombination beginsZygotene- homology search is finalized; homology search is confirmed due to parallel breaking in DNADYADSTETRADS MONADSSPachytene- you can see synaptonemal complex which assures that the pairs do not fall away from one another; not condensed yet. These chromosome pairs are parallel lines lined up calledBIVALENTSDiplotene- you can see the 4 chromatids seperately; chiasmata is visible (points of crossing over) These chaismata can move on the chromatid ; terminalization beginsDiakinesis- tetrads formedDiptotene: Diakinesis:-4 Chromosomes -homologs are- 8 DNA duplexes paired-2n chromosome ploidy- 4n DNA Duplex ploidyDYADS^ Tetrads are presentAnd paired in Meta IMETAPHASE I- tetrads line up in the middle on metaphase plateANAPHASE I- tetrads pull apart & form dyads TELOPHASE I- dyads move to the polesMeioisis I = ___reductional___ division- III. MEIOSIS IIMONADSMeiosis II = _equational _ division- In Animals, meiosis produces: gametesIn Plants, meiosis produces: SporesIV. Sex Determinationa. X -CHROMOSOME-BASEDXX / X O O represents absenxe of chromosome not a shape, so there is no chromosome where O is.XX / XY All mammals are this type – female- XX male- XYPrimary and Secondary Pseudoautosomal are places where the X and Y chromosome areidenticalZZ / ZW birds, snakes, butterflysFemales – ZW Males- ZZHAPLO/DIPLO Bees Female – haplo Male-DiploV. Types of Sex DeterminationENVIRONMENTAL turtles, crocodiles, alligatorsHigh temps – female low temps- malesSEX DETERMINATION IN X/Y SPECIESA study was conducted to determine what made sexes… the presence of the Y or number of X’s- Results found that it was the presense of Y in humans and the ratio of X:Y in drosophilaSEX AUTO RATIO DROS HUMANXX AA 1.0 FEMALE FEMALEXY AA 0.5 MALE MALEX O AA 0.5 MALE FEMALEXXY AA 1.0 FEMALE MALEXXX AA 1.5 FEMALE FEMALEXXXY AA 1.5 FEMALE -XX AAA 0.67 INTERSEX -X O AAA 0.33 METAMALE -VI. What happens when things go wrong?TURNER SYNDROME – sterile, results from a lack of a 2nd chromosome; only female offspring KLINEFELTER SYNDROME – results in infertility, fatty hips and womanly characters with small testes; result of extra X