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Meiosis and Gamete Formation

Meiosis and Gamete Formation

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Meiosis and Gamete Formation

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  1. Meiosis and Gamete Formation

  2. 3 Types of Cell Division • 1. Binary fission-cell division in prokaryotes • 2. Cell Cycle (with Mitosis)-cell division in eukaryotes to form new somatic cells • 3. Meiosis—cell division in eukaryotes to form gametes (egg and sperm)

  3. How are reproductive cells formed? MEIOSIS • Meiosis--cell division that produces reproductive cells called gametes (egg and sperm) • 1 REPLICATION AND *2* DIVISIONS • 46 chromosomes ------------- 23 chromosomes diploid (pairs) MEIOSIS haploid (no pairs) 1somatic (body) cell 4gametes (sex cells) START END Only one set of chromosomes ingametes—no longer in pairs

  4. Body Cells vs. Reproductive Cells SOMATIC CELLS ---- GAMETES DIPLOID MEIOSIS HAPLOID

  5. Think About it!!!! • With meiosis to go from 46  23 chromosomes you end up with: your mom’s egg (23 chromosomes) + your dad’s sperm (23 chromosome) you (46 chromosomes) • WITHOUT MEIOSIS to go from 46  23 chromosomes then it would be…… your mom’s egg (46 chromosomes) + your dad’s sperm (46 chromosomes) 92 AND NO YOU!!!!!!!!!!

  6. Think About it!!!! • With meiosis to go from 46  23 chromosomes you end up with: your mom’s egg (23 chromosomes) + your dad’s sperm (23 chromosome) you (46 chromosomes) • WITHOUT MEIOSIS to go from 46  23 chromosomes then it would be…… your mom’s egg (46 chromosomes) + your dad’s sperm (46 chromosomes) 92 AND NO YOU!!!!!!!!!!

  7. HAPLOID GAMETE (EGG) 23 CHROMOSOMES FIRST DIPLOID CELL OF BABY 46 CHROMOSOMES IN PAIRS!!!! + = HAPLOID GAMETE (SPERM) 23 CHROMOSOMES

  8. What are reproductive cells? • EGGS--In females, body cells in the ovaries called oogonium undergo meiosis to form eggs. • SPERM--In males, body cells in the testicles called spermatogonium undergo meiosis to form sperm.

  9. Spermatogenesis (Meiosis in Males) Spermatogonium 46 SPERM 23 23 23 23

  10. Oogenesis (Meiosis in Females) Oogonium 46 Egg Polar Bodies (not functional) 23

  11. Crossing-Over • Crossing-over during meiosis results in pieces of chromosomes being exchanged. • This leads to great genetic diversity of the egg and sperm that are produced.