1. Copyright © 2005 Pearson Prentice Hall, Inc. Cellular Reproduction Cell division in eukaryotes enables asexual reproduction (F11.1 p. 186)

2. Copyright © 2005 Pearson Prentice Hall, Inc. The parent cell divides into two daughter cells. The plasma membrane grows inward at the middle of the cell. New plasma membrane is added between the attachment points, pushing them further apart. cell division cell growth and DNA replication The DNA replicates and the two DNA double helices attach to the plasma membrane at nearby points. The circular DNA double helix is attached to the plasma membrane at one point. attachment site circular DNA cell wall plasma membrane Cellular ReproductionProkaryotic Cell Cycle: Growth & Binary Fission (F11.2 p187)

3. Copyright © 2005 Pearson Prentice Hall, Inc. G 2 : cell growth G 1 : cell growth and differentiation prophase metaphase anaphase telophase and cytokinesis mitotic cell division interphase S: synthesis of DNA; chromosomes are duplicated G 0 : non- dividing Eukaryotic Cell Cycle: Interphase Cell Division (F11.3 p. 188) Cellular Reproduction Interphase : Cell Grows in Size Replicates Its DNA

4. Copyright © 2005 Pearson Prentice Hall, Inc. DNA in Eukaryotic Cells Is Organized into Chromosomes Eukaryotic Chromosome = 1 Linear DNA Double Helix Bound to Proteins –Chromosome structure (F11.5 p. 190) –Human chromosomes during mitosis (F11.6 p. 191) –(Duplicated) REPLICATED chromosome (F2 p. 191) –Daughter chromosomes (F3 p. 191)

5. Copyright © 2005 Pearson Prentice Hall, Inc. nucleosome: DNA wrapped around histone proteins (10 nm diameter) chromosome: coils gathered onto protein scaffold (200 nm diameter) histone proteins DNA (2 nm diameter) DNA coils coiled nucleosomes (30 nm diameter) protein scaffold

6. Copyright © 2005 Pearson Prentice Hall, Inc. sister chromatidscentromere

7. Copyright © 2005 Pearson Prentice Hall, Inc. genes centromere telomeres

8. Copyright © 2005 Pearson Prentice Hall, Inc. independent daughter chromosomes, each with one identical DNA double helix sister chromatids duplicated chromosome (2 DNA double helices)

9. Copyright © 2005 Pearson Prentice Hall, Inc. DNA in Eukaryotic Cells Is Organized into Chromosomes Eukaryotic Chromosomes: –Usually Occur in Homologous Pairs 1 from Mom & 1 from Dad –Homologs Have Similar (NOT IDENTICAL) Genetic Information Some from Mom & Some from Dad –Karyotype of a human male (F11.7 p. 191)

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11. Cellular Reproduction Two Types of Eukaryotic Cell Division : –Mitotic Cell Division –Meiotic Cell Division Figure 11.4 (Hide/Reveal) Mitotic and meiotic cell division in the human life cycle (p. 189) Unnumbered Figure 1 Chromosome (p. 190)

12. Copyright © 2005 Pearson Prentice Hall, Inc. Mitotic Cell Division Mitotic cell division in an animal cell (F11.8 p. 192)

13. Copyright © 2005 Pearson Prentice Hall, Inc. INTERPHASEMITOSIS LATE INTERPHASE nuclear envelope chromatin nucleolus centriole pairs LATE PROPHASEMETAPHASE beginning of spindle formation kinetochore pole condensing chromosomes spindle microtubules Duplicated chromosomes in relaxed state; duplicated centrioles remain clustered. Chromosomes condense and shorten; spindle microtubules begin to form between separating centriole pairs. Nucleolus disappears; nuclear envelope breaks down; spindle microtubules attach to the kinetochore of each sister chromatid. Kinetochores interact; spindle microtubules line up chromosomes at cell's equator. EARLY PROPHASE

14. Copyright © 2005 Pearson Prentice Hall, Inc. INTERPHASE ANAPHASE "free" spindle fibers chromosomes extending nuclear envelope re-forming Sister chromatids separate and move to opposite poles of the cell; spindle microtubules push poles apart. One set of chromosomes reaches each pole and relaxes into extended state; nuclear envelopes start to form around each set; spindle microtubules begin to disappear. Cell divides in two; each daughter cell receives one nucleus and about half of the cytoplasm. Spindles disappear, intact nuclear envelopes form, chromosomes extend completely, and the nucleolus reappears. TELOPHASE INTERPHASE OF DAUGHTER CELLS CYTOKINESIS

15. Copyright © 2005 Pearson Prentice Hall, Inc. electric pulse fused cells The egg cell without a nucleus and the quiescent udder cell are placed side by side in a culture dish. An electric pulse stimulates the cells to fuse and initiates mitotic cell division. nucleus is removed egg cell DNA donor cell from udder Finn Dorset ewe Cells from the udder of a Finn Dorset ewe are grown in culture with low nutrient levels. The starved cells stop dividing and enter the non-dividing G 0 phase of the cell cycle. Blackface ewe Meanwhile, the nucleus is sucked out of an unfertilized egg cell taken from a Scottish Blackface ewe. This egg will provide cytoplasm and organelles but no chromosomes.

16. Copyright © 2005 Pearson Prentice Hall, Inc. The cell divides, forming an embryo that consists of a hollow ball of cells. The Blackface ewe gives birth to Dolly, a female Finn Dorset lamb, a genetic twin of the Finn Dorset ewe. The ball of cells is implanted into the uterus of another Blackface ewe.

17. Copyright © 2005 Pearson Prentice Hall, Inc. Mitotic Cell Division Prophase –Chromosomes Condense, Spindle Microtubules Form & Attach to the Chromosomes Metaphase – Chromosomes Align Along the Equator of the Cell Anaphase –Sister Chromatids Separate & Pulled to Opposite Poles of the Cell Telophase –Nuclear Envelopes Form Around Both Groups of Chromosomes Cytokinesis –Cytoplasm Is Divided Between Two Daughter Cells –Cytokinesis in an animal cell (F11.9 p. 197) –Cytokinesis in a plant cell (F11.10 p. 197)

18. Copyright © 2005 Pearson Prentice Hall, Inc. The waist completely pinches off, forming two daughter cells. The microfilament ring contracts, pinching in the cell's “waist.” Microfilaments form a ring around the cell's equator.

19. Copyright © 2005 Pearson Prentice Hall, Inc. Complete separation of daughter cells. Vesicles fuse to form a new cell wall (red) and plasma membrane (yellow) between daughter cells. cell wall Golgi complex plasma membrane carbohydrate- filled vesicles Carbohydrate- filled vesicles bud off the Golgi complex and move to the equator of the cell.

20. Copyright © 2005 Pearson Prentice Hall, Inc. Cellular Reproduction Two Types of Eukaryotic Cell Division : –Mitotic Cell Division –Meiotic Cell Division Mitotic & meiotic cell division in human life cycle (F11.4 p. 189)

21. Copyright © 2005 Pearson Prentice Hall, Inc. embryo mitosis, differentiation, and growth meiosis in testes meiosis in ovaries egg sperm adults mitosis, differentiation, and growth fertilization fertilized egg mitosis, differentiation, and growth baby

22. Copyright © 2005 Pearson Prentice Hall, Inc. gene 1gene 2 same alleles different alleles

23. Copyright © 2005 Pearson Prentice Hall, Inc. sister chromatids homologous chromosomes Copyright © 2005 Pearson Prentice Hall, Inc.

24. Meiotic Cell Division Produces Haploid Cells Meiosis Separates Homologous Chromosomes, Producing Haploid Daughter Nuclei Meiotic Cell Division Followed by Fusion of Gametes Keeps the Chromosome Number Constant from Generation to Generation Meiosis I Separates Homologous Chromosomes into Two Haploid Daughter Nuclei –During Prophase I, Homologous Chromosomes Pair Up and Exchange DNA Homologous chromosomes ( F5 p. 198) Two daughter nuclei (F6 p. 198) Four haploid cells (F 7 p. 199) Meiotic cell division (F8 p. 199) Meiotic cell division in an animal cell (F11.11 p. 200)

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27. meiotic cell division fertilization 2n n n

28. Copyright © 2005 Pearson Prentice Hall, Inc. MEIOSIS I recombined chromosomes spindle microtubule paired homologous chromosomes chiasma

29. Copyright © 2005 Pearson Prentice Hall, Inc. MEIOSIS I Prophase I. Duplicated chromosomes condense. Homologous chromosomes pair up and chiasmata occur as chromatids of homologues exchange parts. The nuclear envelope disintegrates, and spindle microtubules form. Metaphase I. Paired homologous chromosomes line up along the equator of the cell. One homologue of each pair faces each pole of the cell and attaches to spindle microtubules via its kinetochore (blue). Anaphase I. Homologues separate, one member of each pair going to each pole of the cell. Sister chromatids do not separate. Telophase I. Spindle microtubules disappear. Two clusters of chromosomes have formed, each containing one member of each pair of homologues. The daughter nuclei are therefore haploid. Cytokinesis commonly occurs at this stage. There is little or no interphase between meiosis I and meiosis II. paired homologous chromosomes recombined chromosomes spindle microtubule chiasma

30. Copyright © 2005 Pearson Prentice Hall, Inc. MEIOSIS II Prophase II. If chromosomes have relaxed after telophase I, they recondense. Spindle microtubules re-form and attach to the sister chromatids. Metaphase II. Chromosomes line up along the equator, with sister chromatids of each chromosome attached to spindle microtubules that lead to opposite poles. Anaphase II. Chromatids separate into independent daughter chromosomes, one former chromatid moving toward each pole. Telophase II. Chromosomes finish moving to opposite poles. Nuclear envelopes re-form, and the chromosomes become extended again (not shown here). Four haploid cells. Cytokinesis results in four haploid cells, each containing one member of each pair of homologous chromosomes (shown here in condensed state).

31. Copyright © 2005 Pearson Prentice Hall, Inc. Meiotic Cell Division Produces Haploid Cells Meiosis I –Metaphase I, Paired Homologs Line Up at the Equator of the Cell –Anaphase I, Homologs Separate –Telophase I, Two Haploid Clusters of Duplicated Chromosomes Form –Mitosis, Meiosis I (F9, 10 p. 202) Meiosis II Separates Sister Chromatids into Four Daughter Nuclei –The mechanism of crossing over (F11.12p. 200) –Comparison of Animal Cell Mitotic & Meiotic Cell Divisions (T11.1 p. 203) –Chromosome configurations at metaphase I F11

32. Copyright © 2005 Pearson Prentice Hall, Inc. Recombination enzymes bind to the joined chromosomes. recombinatio n enzymes Recombination enzymes and protein zippers leave. Chiasmata remain, helping to hold homologous chromosomes together. chiasma Recombination enzymes snip chromatids apart and reattach the free ends. Chiasmata (the sites of crossing over) form when one end of the paternal chromatid (yellow) attaches to the other end of a maternal chromatid (purple). chiasma Duplicated homologous chromosomes pair up side by side. sister chromatids of one duplicated homologue pair of homologous, duplicated chromosomes Protein strands “zip” the homologous chromosomes together. protein strands joining duplicated chromosomes direction of “zipper” formation

33. Copyright © 2005 Pearson Prentice Hall, Inc. spindle microtubules duplicated chromosomes

34. Copyright © 2005 Pearson Prentice Hall, Inc.

35. Why Do So Many Organisms Reproduce Sexually? Mutations in DNA Are the Ultimate Source of Genetic Variability Sexual Reproduction May Combine Different Parental Alleles in a Single Offspring

36. Copyright © 2005 Pearson Prentice Hall, Inc. How Do Meiosis & Sexual Reproduction Produce Genetic Variability? Shuffling of Homologues Creates Novel Combinations of Chromosomes Crossing Over Creates Chromosomes with Novel Combinations of Genes Fusion of Gametes Adds Further Genetic Variability to the Offspring

37. Copyright © 2005 Pearson Prentice Hall, Inc. spindle microtubules duplicated chromosomes

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