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Mitosis

Mitosis. How Cells Reproduce. Types of Cells. The body contains two different types of cells Somatic cells Reproduce by mitosis (asexual reproduction) They are diploid, that is they contain two complete sets of genetic information, (one from each parent) Gametes

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Mitosis

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  1. Mitosis How Cells Reproduce

  2. Types of Cells • The body contains two different types of cells • Somatic cells • Reproduce by mitosis (asexual reproduction) • They are diploid, that is they contain two complete sets of genetic information, (one from each parent) • Gametes • Reproduce by meiosis (sexual reproduction) • They are haploid. Contain only on set of genetic information.

  3. Mitosis • Aged cell transforms itself into twin youthfu cells • Happens millions of times every second in the human body. • It gradually replaces every cell in your body except muscle and nerve cells • In the body, what cells do you think replace themselves the fastest?

  4. The Cell Cycle • The life of a cell can be divided into recurring different time periods called the cell cycle. • Two main parts to the cell cycle. • Interphase • mitosis Fig. 9.3, p. 151

  5. Interphase • The first part of interphase is devided into 4 different parts 1. G1 2. S 3. G2 • Cytokinesis or the division of the cytoplasm Most cells spend most their time (90%) in interphase Fig. 9.3, p. 151

  6. Fig. 9.3, p. 151

  7. centromere one chromatid its sister chromatid one chromosome (in duplicated state) in-text, p. 163

  8. Mitosis • The division of the nucleus is divided into four distinct phases • Prophase • Metaphase • Anaphase • Telephase

  9. Prophase pair of centrioles microtubules kinetochores • Chromosomes start condensing • The spindle starts forming • Centroles start to move to opposite ends of the cells • Microtubules extend out from the centrioles to the kinetochores on each sister chromotid • Nuclear envelope begins to break apart

  10. CELL AT INTERPHASE EARLY PROPHASE LATE PROPHASE PROMETAPHASE cell chromosomes nucleus microtubules pair of centrioles nuclear envelope Fig. 9.5a, p. 152 plasma membrane

  11. Metaphase • Spindle fibers interact to orient chromatids and aligne them at the cell’s equator, halfway between the poles.

  12. Anaphase • The microtubules that are attached to the kinetochores begin to shorten and pull the sister chromotids apart. • One half of each sister chromotide goes to each side of the cell

  13. Telophase • Telophase is the opposite of prophase • Nuclear envelope is reformed • Microtubules are wound up in the centrioles • Chromosomes unwind into chromotine

  14. Cytokinesis (The division of the cytoplasm) • Contractile microfilaments at the cleavage furrow pull the plasma membrane inward. • The membranes come together and pinch off to form new daughter cells

  15. Questions • How many DNA molecules are present in a duplicated chromosome? • What is being separated in anaphase? • What type of cells undergo mitosis? • What is the chromosome number at G1? What is the chromosome number after cytokinesis?

  16. METAPHASE ANAPHASE TELOPHASE INTERPHASE Fig. 9.5b, p. 153

  17. Meiosis The Making of gametes

  18. Meiosis • Meiosis can be broken up into two different parts: Meiosis I and Meiosis II • In meiosis the nucleus devides 2 times, once in meiosis I and again in meiosis II • Meiosis I is broken up into four parts • Prophase I, Metaphase I, Anaphase I and telophase I • Meiosis II also has four different stages. • Prophase I, Metaphase I, Anaphase I and telophase I

  19. Prophase I • The exact same steps that occur in prophase of mitosis occur here. • There are additional steps • Synapsis: Homologous chromosomes come together. • Crossing over takes place

  20. Homologous chromosomes • Homologous chromosomes are chromosomes that code for the same genes • We inherit one homolog from each parent • There are 23 pairs of homologous chromosomes in human somatic cells.

  21. MEIOSIS I PROPHASE I newly forming microtubules in the cytoplasm Homologous Chomosomes come together in a process called synapsis Fig. 10.4a p. 164

  22. Crossing over • During synapsis homologous chromosomes exchange segments of DNA in a process called Crossing over

  23. Meiosis I • In Meiosis I the cell is separating homologous chromosomes. • In Meiosis II the cell is like mitosis in that the cell is separating sister chromotids

  24. MEIOSIS I is separating homologous chromosomes newly forming microtubules in the cytoplasm spindle equator (midway between the two poles) one pair of homologous chromosomes plasma membrane PROPHASE I METAPHASE I ANAPHASE I TELOPHASE I Fig. 10.4a p. 164

  25. MEIOSIS II PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II Fig. 10.4b p. 165

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