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Bio100 (Paddack) Lecture 9 (9/26/16) I. Cell Division: fission & mitosis A. Why B. Asexual vs sexual reproduction C. Prokaryotes: Binary Fission D. Eukaryotes: Cell Cycle 1. Interphase – DNA replication 2. Mitotic Phases a. Prophase b. Prometaphase c. Metaphase d. Anaphase e. Telophase f. Cytokinesis E. Control of Cell Cycle F. When cell cycles go wrong 1. Cancer 2. Mutations II. Sexual reproduction: Meiosis A. Sexual reproduction defined B. Chromosome homologs C. Gametes D. Meiosis process E. How genetic variability arises in meiosis 1. Mutations 2. Random shuffling 3. Random mating 4. Cross over cell division! Chapter 8: Cellular Reproduction Cell division is: • How we get more cells. – growing from a single cell into us – cell renewal and repair • How unicellular organisms reproduce Prokaryotes (bacteria, archaea) reproduce asexually – simple cell division 1 Figure 8.3B Chromosomes DNA molecules Sister chromatids Chromosome duplication Centromere Sister chromatids Chromosome distribution to the daughter cells INTERPHASE Metaphase Prophase Anaphase 2 …and back to INTERPHASE Telophase and Cytokinesis http://vcell.ndsu.nodak.edu/animations/mitosis/movie-flash.htm Mutations: errors in DNA replication Sexual Reproduction Cell types with respect to chromosome number: 1. Somatic cells – all body cells; full number of chromosomes 2. Gametes, germ cells – egg and sperm cells; half the number of chromosomes 1 e.g. 46 + 1 e.g. 46 = 2 e.g. 92 3 • Chromosomes come in pairs Homologous Chromosomes/Homologues – One from egg, one from sperm • Pairs are called Homologous Chromosomes – they hold the same genes 46 chromosomes 23 pairs of chromosomes • carry genes for the same traits. Eye color Tongue rolling Result of Meiosis: 4 haploid gametes (1n) are formed from 1 diploid cell (2n) Meiosis I Meiosis II • Alleles = alternative forms of the same gene Meiosis Diploid = 2N Haploid = N Somatic cells Gametes 4 Meiosis – the production of gametes In Meiosis I: • Homologous chromosomes align • Pairs of homol. chromosomes are separated • In Meiosis II: – Sister chromatids separate (just like mitosis) Figure 8.13 Figure 8.13 http://vcell.ndsu.nodak.edu/animations/downloads/movies/meiosis/MeiosisWMV.wmv Mitosis functions in growth, tissue repair, asexual reproduction occurs in somatic cells Meiosis functions in sexual reproduction occurs only the cells of reproductive tissues to produce gametes produces daughter cells that are genetically identical to parent cell produces daughter cells that have only half the genetic material as the parent cell starts with 1 diploid cell ends with 2 diploid cells starts with 1 diploid cell ends with 4 haploid cells http://www.pbs.org/wgbh/nova/miracle/divi_flash.html 7. What are growth factors and what role do they play? 8. What happens when mitosis becomes uncontrolled? 9. Define: genetic mutation. 10. Define meiosis & state how the end result of it differs from that of mitosis. 11. Define: somatic cell, gamete, diploid, haploid, homologous chromosomes, egg, sperm, fertilization. 12. Are gametes diploid or haploid? 13. The 3 main stages of meiosis are interphase, meiosis I, and meiosis II. Briefly describe overall what happens during each stage. Lecture 9 (9/26/16): Cell Division Study Questions 1. List 3 reasons for cell division. 2. Do prokaryotes under sexual or asexual reproduction? Describe their process of binary fission. 3. Define: mitosis, cell cycle, DNA, chromosome, gene, chromatin, chromatids. 4. There are 2 main stages of mitosis. List them & state what the overall task of each of the 2 stages is. 5. What are sister chromatids? Why do the look like an X when condensed? 6. Sketch each of the following phases of Mitosis & state what is occurring in each: prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis. 14. In prophase of Meiosis I, tetrads are formed – what are they? 15. Crossing over occurs in this stage – what is this and what is the result? 16. List & briefly describe 4 different sources of genetic variability. 5