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MEIOSIS

MEIOSIS. Making gametes…. ASEXUAL REPRODUCTION. Produces cells that are IDENTICAL copies of parent cell; can’t adapt/change EX: Binary fission, budding & regeneration. Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htm. SEXUAL REPRODUCTION.

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MEIOSIS

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  1. MEIOSIS Making gametes…

  2. ASEXUAL REPRODUCTION Produces cells that are IDENTICAL copies of parent cell; can’t adapt/change EX: Binary fission, budding & regeneration Planaria animation: http://www.t3.rim.or.jp/~hylas/planaria/title.htm

  3. SEXUAL REPRODUCTION Family image from: http://babyhearing.org/Parenet2Parent/index.asp Combines genetic material from sperm & egg; offspring are genetically different

  4. ADVANTAGES OF SEXUAL REPRODUCTION Allows for variation in population Allow species adapt to changes in their environment http://naturalsciences.sdsu.edu/classes/lab8/spindex.html

  5. Think-Pair-Share Human body cells contain 46 chromosomes 1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis?

  6. Think-Pair-Share 2. 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?

  7. Think-Pair-Share 3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?

  8. DIPLOID VS HAPLOID Body cells (somatic cells) have 2 copies of each chromosome = DIPLOID (2n) (one from mom; one from dad)

  9. DIPLOID & HAPLOID HAPLOID (1n) Sex cells have only one copy of each chromosome = All sperm and egg cells are haploid

  10. MITOSIS CREATES DIPLOID BODY CELLS • Makes 2 cells genetically identical to parent cell & to each other • Used by organisms to: grow, repair injuries, replace cells http://waynesword.palomar.edu/lmexer2a.htm

  11. MEIOSIS CREATES HAPLOID SEX CELLS • Makes 4 cells genetically different from parent cell & from each other • Used for sexual reproduction http://waynesword.palomar.edu/lmexer2a.htm

  12. HOMOLOGOUS CHROMOSOMES • SAME SIZE & SHAPE • CARRY GENES for the SAME TRAITS • BUT NOT IDENTICAL! http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

  13. Stages of Meiosis

  14. Meiosis

  15. Meiosis takes place in two series of steps No second “I” Meiosis I I, P, M, A, T + Meiosis II P, M, A, T Which means…no DNA replication before meiosis II

  16. Interphase I • DNA replicates creating homologous chromosomes

  17. PROPHASE I • Homologous chromosomes pair up = SYNAPSIS TETRAD =group of FOUR (4) chromatids Images modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif

  18. 2. CROSSING OVER • Exchange of DNA between homologous pairs • After crossing over, chromatid arms are NOT IDENTICAL anymore http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

  19. Metaphase I • Tetrads line up in the middle

  20. Anaphase I- Tetrads pull apart to opposite ends of the cell.

  21. Telophase I- Cell separates into two new cells

  22. Meiosis II No Interphase II = chromosomes are NOT copied again.

  23. Prophase II ~ TWO cells begin meiosis II

  24. Metaphase II chromosomes line up in the middle of the cell

  25. Anaphase II -chromosomes are pulled to opposite ends of the cell

  26. Telophase II / Cytokinesis ~The 2 cells divide to form 4 genetically different cells (gametes)

  27. End Result of Meiosis • Four new cells • Half # chromosomes as parent cell - haploid (n) • Humans – 23 chromosomes

  28. MAKING SPERM & EGGS

  29. SPERMATOGENESIS ___________________= MAKING MATURE SPERM Mature & grow flagella

  30. OOGENESIS __________________ = MAKING a MATURE EGG Produces: 1 “good” egg 3 POLAR BODIES CYTOPLASM DIVIDES UNEVENLY; POLAR BODIES DEGENERATE (DIE)

  31. WHY MAKE ONLY ONE “GOOD” EGG? Sperm donates mostly DNA Most of the cell parts and nutrients needed for baby come from EGG! http://bestweekever.blogs.com/photos/uncategorized/imagemain_sperm_egg1_1.gif

  32. What are the major differences between Mitosis and Meiosis?

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