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Meiosis

Meiosis. Gamete Formation. Vocabulary. Gametes = sex cells (eggs, sperm) Homologous chromosomes = paired chromosomes (maternal and paternal) that have the same genes Haploid = Having only one copy of each chromosome (as opposed to diploid , which has two copies of each).

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Meiosis

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  1. Meiosis Gamete Formation

  2. Vocabulary • Gametes = sex cells (eggs, sperm) • Homologous chromosomes = paired chromosomes (maternal and paternal) that have the same genes • Haploid = Having only one copy of each chromosome (as opposed to diploid, which has two copies of each)

  3. anther (where sperm originate) ovules inside ovary (where eggs originate) Such chromosome pairs are called homologous chromosomes (1) Homologues (2) Alleles - different forms of a gene for a particular trait may occur in homologous chromosomes

  4. Overview of Meiosis A. Meiosis - cell division in which the chromosome number is reduced from diploid and gametes are formed Happens in GAMETES only!!!

  5. Major Events in Meiosis

  6. Meiosis I Produces Diploid Cells

  7. Meiosis II Produces Haploid Cells

  8. Stages of Meiosis TELOPHASE I PROPHASE I METAPHASE I ANAPHASE I A. Prophase I 1. Synapsis - replicated chromosomes form tetrads

  9. TELOPHASE I PROPHASE I METAPHASE I ANAPHASE I B. Metaphase I - tetrads are aligned at the spindle equator

  10. TELOPHASE I PROPHASE I METAPHASE I ANAPHASE I C. Anaphase I - tetrads split and sister chromatids move toward the spindle poles

  11. TELOPHASE I PROPHASE I METAPHASE I ANAPHASE I D. Telophase I - each daughter cell has a haploid chromosome set

  12. PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II E. Meiosis II - sister chromatids separate

  13. Meiosis and Genetic Variation A. Crossing over - the exchange of corresponding segments of homologous chromosomes during prophase I

  14. MitosisandMeiosisCompared

  15. 2. Spermatogenesis - formation of sperm cells secondary spermatocytes (haploid) spermato- gonium (diploid male reproductive cell) primary spermatocyte (diploid) spermatids (haploid) MEITOSIS I, CYTOPLASMIC DIVISION MEIOSIS II, CYTOPLASMIC DIVISION GROWTH a. Results in production of four spermatids

  16. secondary spermatocytes (haploid) spermato- gonium (diploid male reproductive cell) primary spermatocyte (diploid) spermatids (haploid) MEITOSIS I, CYTOPLASMIC DIVISION MEIOSIS II, CYTOPLASMIC DIVISION GROWTH b. Spermatids develop a tail to become mature sperm

  17. 3. Oogenesis - formation of egg cells in females three polar bodies haploid) first polar body haploid) oogonium (diploid reproductive cell) primary oocyte (diploid) secondary oocyte haploid) ovum (haploid) MEITOSIS I, CYTOPLASMIC DIVISION MEIOSIS II, CYTOPLASMIC DIVISION GROWTH a. Results in one large ovum and three polar bodies

  18. MITOSISMEIOSIS One division Two divisions

  19. MITOSISMEIOSIS Two daughter cells Four daughter cells areare produced produced

  20. MITOSISMEIOSIS Daughter cells are Daughter cells contain identical to each other varying combinations of and to parent cell chromosomes

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