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Understanding Meiosis: The Key to Reproduction in All Living Things

Learn about meiosis, the process of making gametes in organisms, and the differences between asexual and sexual reproduction. Explore how meiosis creates genetic diversity and enables species to adapt and evolve. Test your knowledge with self-check questions and understand the significance of genetic recombination during meiosis.

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Understanding Meiosis: The Key to Reproduction in All Living Things

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  1. MEIOSIS Making gametes…

  2. ALL LIVING THINGS __________ REPRODUCE

  3. ASEXUAL REPRODUCTION BINARY FISSION Bacteria reproduce using __________________________________ Budding & regeneration are used by plants and animals to reproduce asexually (mitosis)

  4. ASEXUAL REPRODUCTION- Mitosis - identical Produces cells that are __________ copies of parent cell.

  5. ADVANTAGES OF ASEXUAL REPRODUCTION • Can make offspring faster • Don’t need a partner

  6. DISADVANTAGES OF ASEXUAL REPRODUCTION • ALL ALIKE • Species CAN’T change and adapt • One disease can wipe out whole population

  7. SEXUAL REPRODUCTION-Meiosis - Combines genetic material from 2 parents (sperm & egg) so offspring are genetically ______________from parents DIFFERENT

  8. ADVANTAGES OF SEXUAL REPRODUCTION • Allows for variation in population • Individuals can be different • Provides foundation for EVOLUTION • Allows species to adapt to changes in their environment = +

  9. MEIOSIS is the way… …to make cells with ½ the number of chromosomes for sexual reproduction

  10. Self - Check 1. Human somatic (body) cells have 46 chromosomes. How many do human egg and sperm cells have? 23 chromosomes 2. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis? 3. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo? 4. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have? 46 chromosomes 46 + 46 = 92; a developing embryo would not survive if it contained 92 chromosomes. Sperm and egg should each have 23 chromosomes.

  11. Meiosis Video Best Meiosis Video Ever

  12. DIPLOID & HAPLOID DIPLOID 2n Most cells have 2 copies of each chromosome = ______________ (one from mom; one from dad) All BODY (somatic) cells are diploid HOMOLOGOUSCHROMOSOMES

  13. DIPLOID & HAPLOID HAPLOID 1n Some cells have only one copy of each chromosome = _____________ All sperm and egg cells are haploid

  14. MITOSIS 2 identical • Makes ___ cells genetically _________ to parent cell & to each other • Makes ___ cells • Makes __________________ • Used by organisms to: increase size of organism, repair injuries, replace worn out cells 2n SOMATIC (body cells)

  15. MEIOSIS 4 • Makes ____ cells genetically different from parent cell & from each other • Makes _____ cells • Makes ___________________ • Used for _______________ 1n Gametes (sperm & eggs) sexual reproduction

  16. Meiosis Vocabulary Asexual Reproduction Sexual Reproduction Haploid Diploid Homologous Chromosomes Gametes Somatic Cells

  17. WHAT MAKES MEIOSIS DIFFERENT ? • SYNAPSIS & CROSSING OVER (PROPHASE I) 2. SEGREGATION & INDEPENDENT ASSORTMENT (ANAPHASE I) 3. Skip INTERPHASE II (NO S) CELL DIVIDES TWICE, BUT… ONLY COPIES DNA ONCE

  18. WHAT MAKES MEIOSIS DIFFERENT ? • Homologous chromosomes pair up during ________________ PROPHASE I This group of FOUR (4) chromatids is called a _________________ TETRAD

  19. WHAT MAKES MEIOSIS DIFFERENT? CROSSING OVER 1. Exchange of DNA betweenhomologous pairs = _____________during PROPHASE I Allows shuffling of genetic material

  20. HOMOLOGOUS CHROMOSOMES • SAME SIZE • SAME SHAPE • CARRY GENES for the SAME TRAITS • BUT __________________! NOT IDENTICAL

  21. CROSSING OVER • Allows for_________________ in different combinations • After crossing over, chromatid arms are________________ anymore rearranging of DNA NOT IDENTICAL http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

  22. WHAT MAKES MEIOSIS DIFFERENT ? 2.Separation during ANAPHASE I SEGREGATION & INDEPENDENT ASSORTMENT Separates gene choices and allows shuffling of genetic material

  23. SEGREGATION(Anaphase I)

  24. SEGREGATION & CROSSING OVERtogether make even more combinations See ananimation

  25. INDEPENDENT ASSORTMENT

  26. INDEPENDENT ASSORTMENTat ANAPHASE I The random distribution of csomes in the formation of gametes This is why you don’t look exactly like your brothers and sisters even though you share the same parents!

  27. http://www.tokyo-med.ac.jp/genet/anm/mimov.gi

  28. WHAT MAKES MEIOSIS DIFFERENT ? Crossing over Segregation Independent assortment ALL are ways MEIOSIS results in =______________________________ So daughter cells are ______________ from parents and from each other GENETIC RECOMBINATION different

  29. WHAT MAKES MEIOSIS DIFFERENT ? 3. Skip INTERPHASE II (No S) CELL DIVIDES TWICE, BUT …ONLY COPIES ITS DNA ONCE MITOSIS: P M A C G1 T S G2        MEIOSIS: ( I ) G1 A T C S G2 P M        ( II ) A P M T C    

  30. Figure 11-15 Meiosis • Section 11-4 • Meiosis I

  31. Figure 11-17 Meiosis II • Section 11-4 • Meiosis II • Prophase II • Metaphase II • Anaphase II • Telophase II • Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. • The chromosomes line up in a similar way to the metaphase stage of mitosis. • The sister chromatids separate and move toward opposite ends of the cell. • Meiosis II results in four haploid (N) daughter cells.

  32. Meiosis Vocabulary Crossing Over Meiosis One Meiosis Two Independent Assortment

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