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Meiosis - Reproductive Cell Division

Meiosis is a cell division process that produces sex cells (gametes). It involves the separation of homologous chromosomes and results in the production of haploid cells. This process occurs in reproductive organs and is essential for the formation of sperm and eggs. Meiosis leads to genetic variation and is crucial for the continuity of a species.

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Meiosis - Reproductive Cell Division

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  1. Meiosis - Reproductive Cell Division • Meiosis = cell division during which sex cells (gametes) are produced • Remember: sex cells contain half the number of chromosomes as the body cells (haploid) • Male gametes = sperms (1n) ** n = # of chromosomes • Female gametes = eggs (1n) • Fertilization = uniting of male and female gametes; resulting fertilized egg = zygote (2n) 1n (egg) + 1n (sperm) = 2n (offspring)

  2. sperm n=23 n=23 egg 2n=46 zygote Fertilization

  3. Meiosis Cont. • Occurs only in reproductive organs called gonads (testes or ovaries) • Meiosis in males = spermatogenesis (gives rise to sperms) • Meiosis in females = oogenesis (gives rise to eggs)

  4. Karyotype= collection of all organism’s chromosomes

  5. Meiosis I Meiosis II Diploid Haploid Haploid Overview of Meiosis Sister chromatids separate Homologous chromosomes separate Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Telophase II Results of meiosis:4 haploid cells are produced from one diploid cell

  6. Spindle fibers Nucleus Nuclear envelope Prophase I (early) (diploid) Prophase I (late) (diploid) Metaphase I (diploid) Anaphase I (diploid) Telophase I (diploid) Meiosis I : homologous chromosomes separate

  7. Four nonidentical haploid daughter cells Prophase II (haploid) Metaphase II (haploid) Anaphase II (haploid) Telophase II (haploid) Meiosis II : sister chromatids separate

  8. Why do we have meiosis? I. To make sperm and eggs II. To make new combinations of genes (due to crossing over and independent assortment of chromosomes) which leads to variation within a species

  9. Homologous chromosomes Tetrad

  10. Tetrad Genetic variation

  11. Random (independent) assortment

  12. CELL DEATH 2 types of cell death: • Orderly, genetically programmed cell death = apoptosis • Cell death due to injury = necrosis

  13. CELL AGING • Geriatrics = branch of medicine dealing with medical problems of elderly As we age: • Many vital functions slow down • Telomeres (DNA on tips of chromosomes) shorten • Glucose is added to proteins and contributes to stiffening • Free radicals damage proteins, lipids, and DNA

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