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MITOSIS AND MEIOSIS

Discover the processes of mitosis and meiosis in cell division, including stages, purposes, and genetic variations. Explore how these divisions create offspring and gametes for sexual reproduction.

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MITOSIS AND MEIOSIS

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  1. MITOSIS AND MEIOSIS Cell Division

  2. MITOSIS • ASEXUAL division of a cell • Occurs in EUKARYOTIC cells (they HAVE a nucleus) • Makes a clone • A CLONE is a genetically identical copy

  3. MITOSIS • Produces offspring with the full DIPLOID number of chromosomes. • Ex. In a fruit fly, there are 8 chromosomes, so our diploid number (2n) is 8. 2n 2n 2n

  4. MITOSIS • “Offspring” (daughter cells) are genetically identical to the “parent” cell. • In humans, mitosis is used for growth and repair of body tissues. • Ex. If you have a cut, mitosis is what helps the cut to heal.

  5. MITOSIS • Picture

  6. STAGES OF MITOSIS • INTERPHASE • This “stage” is where the cell spends most of it’s “life”. • The cell prepares for division by making an exact copy of each chromosome. (replication)

  7. STAGES OF MITOSIS • PROPHASE • The chromosomes become visible. • The nuclear membrane begins to disappear. • The SPINDLE FIBERS form between CENTRIOLES.

  8. STAGES OF MITOSIS • METAPHASE • The chromosomes “line up” in the middle of the spindle. • Spindles attach to centromere

  9. STAGES OF MITOSIS • ANAPHASE • The chromosomes begin to separate • When they separate, each piece becomes a CHROMATID.

  10. STAGES OF MITOSIS • TELOPHASE (in ANIMAL cells) • Two new cells begin to form by pinching in (cleavage) at the membrane. • CYTOKINESIS-the division of cytoplasm

  11. STAGES OF MITOSIS • TELOPHASE (in PLANT cells) • Instead of pinching in, a CELL PLATE forms between the two daughter cells.

  12. 3 REASONS MITOSIS OCCURS • 1. As the cells divide, the organism increases in size. • 2. In humans, mitosis occurs to replace dead red blood cells (about every 120 days). • 3. Asexual cellular reproduction • Ex. Amoeba

  13. MITOSIS PICTURES

  14. MITOSIS PICTURES

  15. MEIOSIS • Sexual reproduction (involves 2 parents) • Makes sex cells (gametes) • These gametes are • ___________________(male) • ___________________(female) • The gametes are made in the gonads. • The gonads are • _______________________(males) • _______________________(females)

  16. MEIOSIS • All meiosis occurs in the GONADS • Purpose: • To reduce the chromosome number so when 2 gametes combine (fertilization), a zygote is formed.

  17. MEIOSIS • Picture of GAMETOGENESIS

  18. MEIOSIS • Oogenesis • Occurs in the _______________ • Forms of 1 egg and 3 polar bodies • The egg has half the chromosome number as the parent cell. (haploid number) • Spermatogenesis • Occurs in the _______________ • Produces 4 sperm cells • Each sperm has half the chromosome number of the parent cell. (haploid number)

  19. MEIOSIS • Chromosome numbers are reduced during meiosis. • Examples: • If a body cell has 46 chromosomes, the gamete will have _______. • If a dog’s skin cell has 72 chromosomes, each sperm cell will have _______. • If a liver cell has 32 chromosomes, how many chromosomes does the egg cell have? _____ • If an alligator has 14 chromosomes in its sperm, how many chromosomes are in his mates egg cell? ______ • If the haploid number is 23, then the diploid number is _____.

  20. MEIOSIS • Recombination of chromosomes causes GENETIC VARIATION. • Picture of fertilization

  21. MEIOSIS • Meiosis is called reduction-division of chromosomes because the chromosome number is reduced and replicated before the cell divides. • Diploid  Haploid • 2N  N

  22. MEIOSIS • Steps of meiosis: Meiosis I and Meiosis II • During Meiosis I- • Interphase • Chromosomes pair up to form homologous pairs. • Prophase • Spindle forms and nuclear membrane disappears • Metaphase • Homologous Pairs line up in the middle of the spindle • A TETRAD is formed (sister chromatids) • This is called SYNAPSIS • Genetic information is shared • Anaphase • Homologous Pairs are separated from one another • This is called DISJUNCTION • Telophase • Cytoplasm divides • Each cell has the monoploid (haploid) number of chromosomes

  23. MEIOSIS • Steps of meiosis: Meiosis I and Meiosis II • During Meiosis II- • Prophase II • Spindle forms and nuclear membrane disappears • Metaphase II • Chromosomes line up in the middle of the spindle. • Anaphase II • Chromosomes are pulled apart by spindles. • Telophase II • Cytokinesis (cytoplasm divides) and four DAUGHTER CELLS are formed (in males).* • *In females, only ONE viable monoploid cell is produced.

  24. MEIOISIS

  25. MEIOSIS

  26. MITOSIS AND MEIOSIS

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