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Cell Division (part 5): Meiosis

Students should be able to: <br>- identify, with the aid of diagrams, the main stages of meiosis (names of the sub-divisions of prophase are not required) <br>- define the terms haploid and diploid, and explain the need for a reduction division process prior to fertilisation in sexual reproduction <br>- state how meiosis and fertilisation can lead to variation

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Cell Division (part 5): Meiosis

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  1. Meiosis Chapter 16

  2. Meiosis

  3. Lesson Objectives (a) identify, with the aid of diagrams, the main stages of meiosis (Names of the sub-divisions of prophase are not required) (b) state how 1meiosis and 2fertilisation can lead to variation Use the knowledge gained in this section in new situations or to solve related problems.

  4. Recap Mitosis Meiosis Same no. as parents Half the no. of chromosomes Same/different no. of chromosomes (with regards to their parent cells) Genetically identical to parent cell? Genetically identical Genetic variation

  5. How do we remember the stages of the cell cycle? I nterphase P rophase M etaphase M A naphase T elophase C ytokinesis

  6. Overview of Mitosis

  7. Mitosis vs. Meiosis: Side by Side Comparison

  8. Overview of Meiosis • Is a form of nuclear division such that the daughter nuclei produced contain half the number of chromosomes as the parent nuclei • consists of 2 stages: Meiosis I and Meiosis II

  9. Meiosis I (pg. 308 Bio Textbook))

  10. Meiosis II

  11. Questions: • Is there any similarity between meiosis and mitosis? • State the 2 processes that take place in meiosis that brings about genetic variation.

  12. How is prophase I of meiosis different from prophase of mitosis? 1. Homologous chromosomes pair up (synapsis) forming a tetrad (a.k.a. bivalent) 2. Formation of chiasmata. Crossing over takes place

  13. Chiasmata (plural) (singular)

  14. Crossing Over

  15. Independent Assortment

  16. Sperm production 23 chromosomes haploid (n) 23 chromosomes haploid (n) 46 chromosomes diploid (2n) 23 chromosomes haploid (n) 23 chromosomes haploid (n) Definition of gamete: A reproductive cell containing the haploid number of chromosomes

  17. Production of Eggs 23 chromosomes haploid (n) 46 chromosomes diploid (2n) Variations in the gametes, together with random fertilization produce variations in the offspring

  18. Sexual Reproduction fertilization zygote (2n) ovum (n) Sperm (n) + mitosis formed by meiosis in the gonads, testes and ovary embryo (2n) where n = haploid; 2n = diploid

  19. That is why…

  20. Mitosis vs Meiosis

  21. Test yourself • Attempt the MCQ worksheet given to you to assess your understanding of the lesson

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