PLB 115 1st Edition Lecture 13Cell DivisionPrevious Notes’ OutlineI. Embryonic Sexual DevelopmentII. X & YIII. Sex DeterminationIV. Sexual MaturationV. Male Reproductive SystemVI. Spermatogenesisa. SpermVII. Female Sexual MaturationVIII. Female Reproductive SystemIX. OvulationX. Hormonesa. Hormonal CycleXI. FertilityXII. ContraceptionXIII. FertilizationXIV. PregnancyXV. Embryonic DevelopmentXVI. TwinsXVII. BirthCurrent Notes’ OutlineI. Down SyndromeII. Abnormalities & Non-disjunctionIII. Gamete ProductionIV. Meiosis I (PMAT1)a. Prophase Ib. Metaphase Ic. Anaphase Id. Telophase IV. CytokinesisVI. Meiosis IIa. Prophase IIb. Metaphase IIc. Anaphase IIThese 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.d. Telophase IIVII. Sexual ReproductionVIII. Mitosisa. Interphasei. G1ii. Siii. G2IX. Prophasea. Late prophaseX. MetaphaseXI. AnaphaseXII. TelophaseXIII. CytokinesisXIV. Mitosis vs MeiosisCell ReproductionDown Syndrome/Trisomy 21- Non-disjunction in Anaphase leaves chromosome 21 with three copies of chromosomeso 47 instead of the normal 46 chromosomesPeople with Down Syndrome have….- Thickened eyelids- Mental impairment - Faulty speechAbnormalities & Non-disjunction- Nondisjunction occurs when homologous chromosomes do not separate during cell divisiono Often leads to death (before birth) in human embryoso Only some (Trisomy 21) live while monosomy (one pair of chromosomes) livesGamete Production- 2 cell divisions- Meiosis 1 & Meiosis II (reduction division from diploid to haploid)- Produces 4 haploid cells- Meiosis 1 begins first after cell replicationMeiosis I (PMAT1)Prophase I- Homologous chromosomes move toward one another & pair up- Crossing over & exchange of equivalent DNA bits occuro Creates new, different genes that can never be replicated & passed uniquely to next generationMetaphase I- Homologous chromosomes move to equatorial plate & pair up randomly Homologous vs Non-homologous Chromosomes- Homologous Chromosomes- Same order of genes along their DNA sequence- Same size, centromere in same locationo One pair from mom, other from dad- Non-homologous chromosomes o Have different genes on their DNAAnaphase I- Homologous pairs separate o Segregation: Homologous pairs move to opposite poles (one to each)- Chromosome # reduced to haploid (from diploid)- Independent Assortment: Each homologous pair separates independently of the othersTelophase I- Chromosomes uncoil to go back to chromatin- Nuclear membrane reforms- Spindle fibers disappearCytokinesis- Divides two haploid nuclei into 2 daughter cellsMeiosis II (PMAT II)Prophase II- Similar to mitosis prophase- Nuclear membrane disassembles- Spindle fibers begin to formMetaphase I- Chromosomes line up at the equatorial plateAnaphase I- Centromeres break apart- Sister chromatids separateo Now daughter chromosomesTelophase I- Similar to cytokinesis in Mitosis: Daughter cells separateSexual Reproduction- Meiosis makes haploid gametes that have only ½ future individual’s genetic material- Egg & sperm join in fertilization & zygote gets ½ genetic info from egg, ½ from sperm - Eggs in animal ovaries, Pistils in plants- Sperm in animal testes, Anthers in plantsMitosis- Somatic cell divisionOccurs in four phases: (Interphase) ProphaseMetaphaseAnaphaseTelophase& then cytokinesis that divides the cytoplasm of enlarged cell into two new daughter cells Interphase - Metabolism & more to prepare for next cell division- Three phasesG1 Phase- The cell gathers nutrients, carries out its regular metabolic roles, performs its normal function- Prepares to divide (Some cells never divide; they stay in G1, called Go)- Prepares for DNA replicationsS Phase- DNA Replication- DNA in chromosomes wrapped around (histones) + histones = chromatin- Identical copies of chromosomes are connected togethero Each copy= sister chromatid & both are connected to each other at centromereG2 Phase- Final preparations for Mitosis- Proteins are made that will move and separate the chromosomesProphase- Thin, long, tangled chromatin uncoils & thickens to chromosomes- Nuclear membranes disassemble- Spindle fibers begin to form(Late prophase)- Spindle fibers (made of microtubules that form in centrioles) attach to chromosomes at their centromeres& move chromosomes aroundMetaphase- Spindle fibers move chromosomes to be at the middle of the cell (the equatorial plate)Anaphase- Sister chromatids separate and move toward opposite poles (future daughter chromosomes) as the kinetochore (proteins attached at the centromere) pulls the chromatid along the spindle fiberTelophase- Spindle fibers disassemble- Nuclear membranes form around the two new sets of chromosomes- Chromatin uncoils- Nucleolus reforms- The daughter cells enter interphase againCytokinesis- Separates two new nuclei into 2 new cells- Divides cytoplasm in ½In animal cells:- Membrane forms a cleavage furrow - Cell pinches into twoIn plant cells:- Cell plate is formed- New cell wall is built, separating the nucleiMitosis vs