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Semester 1, Day 7

Semester 1, Day 7. Meiosis. Agenda. Study for Virus Quiz Turn in Virus Homework (18.1 and 18.2) Virus Quiz Lecture and Activity for Meiosis Practice Meiosis Reading/Work Time for Meiosis Review Meiosis Questions. Study. Reasons why viruses are non-living Parts of a virus

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Semester 1, Day 7

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  1. Semester 1, Day 7 Meiosis

  2. Agenda • Study for Virus Quiz • Turn in Virus Homework (18.1 and 18.2) • Virus Quiz • Lecture and Activity for Meiosis • Practice Meiosis • Reading/Work Time for Meiosis • Review Meiosis Questions

  3. Study • Reasons why viruses are non-living • Parts of a virus • Diagram of virus cycles • Steps of virus cycles

  4. Homework to Turn In • Cornell Notes: Section 18.1, 18.2 • Questions: • Section Assessment 18.1: #1-6 • Section Assessment 18.2: #1-6 • Chapter 18 Assessment: #1-17, 19-26

  5. Quiz • Viruses

  6. Reproduction & Genetic Material • Production of Offspring • Asexual: 1 parent, genetically identical offspring • Prokaryotic organisms, some plants • Sexual: 2 parents (1/2 DNA from each), genetically different offspring “Not” Fertilization First cell of an organism Sperm (Male) Ovum (Female) Zygote (Fertilized Ovum) Gametes: sex cells

  7. Reproduction & Genetic Material • Recall: DNA = genetic information DNA doesn’t naturally occur like this! Chromosome: coiled DNA Image Source: www.riversideonline.com

  8. Reproduction & Genetic Material • Unduplicated vs. Duplicated Chromosomes Image Source: histology.kasralainy.edu.eg

  9. Chromosomes • Genes: Portion of DNAthat codes for a protein • Homologous Chromosomes: a pair of chromosomes of the same length, same centromere position, and carry genes that control the same traits. One chromosome from each parent makes a pair. • Chromosome Number: Humans have 23 homologous pairs Different Genes From Mom From Dad Same centromere position Same Length Genes that control a trait (ex. eye color)

  10. Chromosomes • Karyotype: number & visual appearance of chromosomes in an organism • Sex Chromosomes: • 23rd “pair” • Female: X X • Male: X Y Image Source: www.biotechnologyonline.gov.au

  11. Chromosomes • What would happen if human gametes each had 46 chromosomes? • Therefore… Gametes must have half (23) of the chromosomes! Fertilization Fertilization 46 23 46 92 23 46 Can’t be human! Human! Male Male Female Female Zygote Zygote

  12. Chromosomes • Let’s represent the # of chromosomes in a gamete for ANY organism as “n”. Fertilization n 2n n All Sexual Reproduction Male Female Zygote “Haploid” = n Gk. Haplos = Single “Diploid” = n Gk. Diplos = Double

  13. Chromosomes • You receive one chromosome for every homologous pair from each parent. Mom (2n) Dad (2n) Pass on “n” Pass on “n” Child (2n)

  14. Make your own chromosomes • You have 4 small, 4 medium, and 4 large chromosomes • Decorate 2 small, 2 medium, and 2 large for MOM • All should be identical • Example: polka dots • Decorate 2 small, 2 medium, and 2 large for DAD • All should be identical • Example: stripes

  15. Meiosis • Mom and Dad are both “2n”. How do they make gametes of “n”? Mom Dad 2n 2n • Process? = MEIOSIS • Cell division that halves the chromosome number. Creates gametes for sexual reproduction. n Process? Process? n Sperm Ovum Fertilization 2n Child

  16. Meiosis PMAT I PMAT II

  17. Meiosis • Meiosis I: 1st Cell Division • Meiosis II: 2nd Cell Division Gametes (become sperm or ovum) Meiosis I Meiosis II Body Cell 2n (Diploid) n (Haploid) n (Haploid)

  18. Meiosis Your Body Cell (2n) Single Chromatids Ignore other organelles for now Gap 1 • Interphase (before division): preparing for cell division • G1 Phase (Gap 1) • Cell is growing • Normal functions • Prepping for DNA duplication • S Phase (Synthesis) • DNA is copied • Single chromatids  Sister chromatids • G2 Phase (Gap 2) • Cell continues growing • Prepping for cell division DNA is uncondensed (not in chromosomes) and is called chromatin Synthesis Gap 2 Your Body Cell (2n) Sister Chromatids Act this out with our chromosomes

  19. Centrioles: organize cell during division Meiosis • Meiosis I: 1 cell  2 cells • Prophase I • Chromatin condenses into chromosomes • Homologous chromosomes pair up; crossing over occurs • Nuclear envelope breaks down • Spindle fibers form from the centrioles From your dad From your mom Crossing Over Your Body Cell (2n) Sister Chromatids Nuclear Envelope **Recall: In humans, 23 pairs of homologous chromosomes in a human (2n = 46). Here, we are using 2 pairs (2n = 4). Homologous Chromosomes Genetic information exchanges = increased variation Act this out with our chromosomes Image Source: legacy.owensboro.kctcs.edu

  20. Equator Meiosis • Meiosis I (cont.) • Metaphase I • Spindle fibers attach to centromeres of chromosomes • Homologous pairs line up at equator of cell • Anaphase I • Homologous chromosomes separate and move along spindle fibers to opposite poles Your Body Cell (2n) Sister Chromatids (n) at each pole (n) at each pole Your Body Cell (2n) Sister Chromatids Act this out with our chromosomes

  21. Meiosis • Meiosis I (cont.) • Telophase I • Spindles break down • Chromosomes uncoil, nuclei reform • Cell divides into two Cytokinesis (n) Chromosomes Sister Chromatids (n) Chromosomes Sister Chromatids Act this out with our chromosomes

  22. Meiosis • Meiosis II: 2 cells  4 cells • Prophase II • Chromatin condenses into chromosomes (again!) • Nuclear envelopes break down (again!) • Spindle fibers form from centrioles (again!) and attach to chromosomes • Metaphase II • Centromeres of chromosomes line up at equator of each cell (not in pairs!) (n) Chromosomes Sister Chromatids (n) Chromosomes Sister Chromatids Equators (n) Chromosomes Sister Chromatids (n) Chromosomes Sister Chromatids Act this out with our chromosomes

  23. Meiosis (n) at each pole (n) at each pole • Meiosis II (cont.) • Anaphase II • Centromeres split • Sister chromatids separate & move to opposite poles • Telophase II • 4 nuclei reform • Spindles break down • Chromosomes uncoil • Cells divide (n) Chromosomes Single Chromatids (n) Chromosomes Single Chromatids (n) at each pole (n) at each pole Cytokinesis Act this out with our chromosomes

  24. Meiosis • Final Products Meiosis Spermatogenesis Oogenesis Act this out with our chromosomes

  25. Meiosis • Spermatogensis • In males, only a special diploid (2n) cell called spermatocyte in a testis can undergo meiosis to create a sperm. 4 sperm cells are formed. Image Source: www.mun.ca

  26. Meiosis • Oogensis • In females, only a special diploid (2n) cell called an oocyte in an ovary can undergo meiosis to create an ovum. 1 ovum is formed, 3 polar bodies that die are also formed. Image Source: www.mun.ca

  27. Practice • Show me: • Interphase, G1 • Interphase, G2 (Assume Interphase S occurred) • Prophase I • Metaphase I • Anaphase I • Telophase I • Prophase II • Metaphase II • Anaphase II • Telophase II • Show me: • Metaphase II • Prophase I • Interphase G1 • Anaphase II • Prophase II • Telophase I • Interphase G2 (Assume Interphase S occurred) • Anaphase I • Telophase II • Metaphase I

  28. Reading/Work Time • Cornell Notes on Section 10.2 (Meiosis) • 10.2 Section Assessment: • #1-5 • Chapter 10 Assessment: • #1, 4-6, 9, 10, 13, 15, 18, 25, 26-28, 30

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