Principles of Biology ______Lake Tahoe Community College s3

Lake Tahoe Community College Bio 101 Fall Qtr Instructor: Sue Kloss ______

Chapter 13 - Meiosis ______

I. Units of heredity A. Genes are segments of DNA (chromosomes) 1. genes 2. gametes 3. somatic cells 4. locus B. Asexual vs. sexual reproduction 1. asexual repro a. protists b. genomes c. some multicellular organisms d. clones 2. sexual repro II. Meiosis and fertilization alternate in sexual life cycles A. somatic cells 1. life cycle 2. homologous chromosomes 3. karyotype B. gametes have a single set of chromosomes 1. 1n v 2n (haploid v diploid) 2. humans diploid number 3. germ cells v gametes v somatic cells 4. sex chromosomes v autosomes 5. sex - haploid sperm joins w/ haploid egg 6. fertilization 7. zygote C. Variety of sexual life cycles 1. life cycle 2. timing of events 3. 3 main types of life cycles a. animals b. plants and some algae c. most fungi and some protists 4. All of these types of sexual repro produce genetic variation III. Meiosis A. Meiosis stages: Meiosis I – separate the homologs; Meiosis II – separate the sister chromatids 1. interphase 2. Prophase I - occupies 90% of meiosis 3. metaphase I - 4. anaphase I 5. telophase I and cytokinesis 6. Rest of meiosis is similar to mitosis: Prophase II. 7. Metaphase II 8. Anaphase II 9. Telophase and cytokinesis II B. Comparison of mitosis and meiosis 1. daughter cells 2. number of chromosome sets 3. Three events unique to meiosis, occur during meiosis I 4. meiosis is called reductional division 5. mechanism for separating sister chromatids is virtually identical in meiosis II and mitosis IV. Genetic variation formed in sexual reproduction contributes to evolution A. mutations B. every individ having own unique combo of genes C. 3 mechanisms contribute to genetic variation arising from sexual repro 1. independent assortment 2. crossing over 3. random fertilization D. Why genetic variation is important

Lesson Objectives/Homework Chapter 13

1. Explain in general terms how traits are transmitted from parents to offspring. 2. Distinguish between asexual and sexual reproduction. 3. Distinguish between the following pairs of terms: 4. Explain how haploid and diploid cells differ from each other. State which cells in the human body are diploid and which are haploid. 5. Explain why fertilization and meiosis must alternate in all sexual life cycles. 6. Distinguish among the three life-cycle patterns characteristic of eukaryotes, and name one organism that displays each pattern. 7. Draw and label the phases of meiosis I and meiosis II and describe the events characteristic of each phase. 8. Identify the phases of meiosis from diagrams or photographs. 9. Draw and describe the process of synapsis during prophase I and explain how genetic recombination occurs. 10. Describe three events that occur during meiosis I but not during mitosis 11. Explain the processes of independent assortment, crossing over, and random fertilization, and describe how they contribute to genetic variation in sexually reproducing organisms. 12. Explain why heritable variation is crucial to Darwin‘s theory of evolution by natural selection.