Chapter 9 Cellular Reproduction

1. Chapter 9 Cellular Reproduction Section 1: Cellular Growth Section2: Mitosis and Cytokinesis Section 3: Cell Cycle Regulation 10.1: Meiosis

2. Cellular Reproduction Chapter 9 9.1 Cellular Growth Ratio of Surface Area to Volume

3. Cellular Reproduction Chapter 9 9.1 Cellular Growth • As the cell grows, its volume increases much more rapidly than the surface area. • The cell might have difficulty supplying nutrients and expelling enough waste products.

4. Cellular Reproduction Chapter 9 9.1 Cellular Growth Transport of Substances • Substances move by diffusion or by motor proteins. • Diffusion over large distances is slow and inefficient. • Small cells maintain more efficient transport systems.

5. Cellular Reproduction Chapter 9 9.1 Cellular Growth Cellular Communications • The need for signaling proteins to move throughout the cell also limits cell size. • Cell size affects the ability of the cell to communicate instructions for cellular functions.

6. Cellular Reproduction Chapter 9 9.1 Cellular Growth The Cell Cycle • Cell division prevents the cell from becoming too large. • It also is the way the cell reproduces so that you grow and heal certain injuries. • Cells reproduce by a cycle of growing and dividing called the cell cycle.

7. Cellular Reproduction Chapter 9 9.1 Cellular Growth • Interphase is the stage during which the cell grows, carries out cellular functions, and replicates. • Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide. • Cytokinesisis the method by which a cell’s cytoplasm divides, creating a new cell.

8. Cellular Reproduction Chapter 9 9.1 Cellular Growth The Stages of Interphase • The first stage of interphase, G1 • The cell is growing, carrying out normal cell functions, and preparing to replicate DNA.

9. Cellular Reproduction Chapter 9 9.1 Cellular Growth The Second Stage of Interphase, S • The cell copies its DNA in preparation for cell division.

10. Cellular Reproduction Chapter 9 9.1 Cellular Growth The Third Stage of Interphase, G2 • The cell prepares for the division of its nucleus.

11. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis The Stages of Mitosis • Prophase • The cell’s chromatin tightens. • Sister chromatids are attached at the centromere. • Spindle fibers form in the cytoplasm.

12. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis • The nuclear envelope seems to disappear. • Spindle fibers attach to the sister chromatids.

13. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis Metaphase • Sister chromatids are pulled along the spindle apparatus toward the center of the cell. • They line up in the middle of the cell.

14. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis Anaphase • The microtubules of the spindle apparatus begin to shorten. • The sister chromatids separate. • The chromosomes move toward the poles of the cell.

15. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis Telophase • The chromosomes arrive at the poles and begin to relax. • Two new nuclear membranes begin to form and the nucleoli reappear. • The spindle apparatus disassembles.

16. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis Cytokinesis • In animal cells, microfilaments constrict, or pinch, the cytoplasm. • In plant cells, a new structure, called a cell plate, forms.

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18. Cellular Reproduction Chapter 9 9.3 Cell Cycle Regulation Normal Cell Cycle • Different cyclin/CDK combinations signal other activities, including DNA replication, protein synthesis, and nuclear division throughout the cell cycle.

19. Cellular Reproduction Chapter 9 9.3 Cell Cycle Regulation Quality Control Checkpoints • The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong. • Spindle checkpoints also have been identified in mitosis.

20. Cellular Reproduction • Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function. Chapter 9 9.3 Cell Cycle Regulation Abnormal Cell Cycle: Cancer • Cancer is the uncontrolled growth and division of cells.

21. Cellular Reproduction Chapter 9 9.3 Cell Cycle Regulation Causes of Cancer • The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations. • Various environmental factors can affect the occurrence of cancer cells.

22. Cellular Reproduction Chapter 9 9.3 Cell Cycle Regulation Apoptosis • Programmed cell death • Cells going through apoptosis actually shrink and shrivel in a controlled process.

23. Cellular Reproduction Chapter 9 9.3 Cell Cycle Regulation Stem Cells • Unspecialized cells that can develop into specialized cells when under the right conditions

24. Cellular Reproduction Chapter 9 9.3 Cell Cycle Regulation Embryonic Stem Cells • After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells. These cells have not become specialized.

25. Cellular Reproduction Chapter 9 9.3 Cell Cycle Regulation Adult Stem Cells • Found in various tissues in the body and might be used to maintain and repair the same kind of tissue • Less controversial because the adult stem cells can be obtained with the consent of their donor Cellular Reproduction

26. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Chromosomes and Chromosome Number • Human body cells have 46 chromosomes • Each parent contributes 23 chromosomes • Homologous chromosomes—one of two paired chromosomes, one from each parent

27. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Chromosomes and Chromosome Number • Same length • Same centromere position • Carry genes that control the same inherited traits

28. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Haploid and Diploid Cells • An organism produces gametes to maintain the same number of chromosomes from generation to generation. • Human gametes contain 23 chromosomes. • A cell with n chromosomes is called a haploid cell. • A cell that contains 2n chromosomes is called a diploid cell.

29. Sexual Reproduction and Genetics • When gametes combine in fertilization, the number of chromosomes is restored. Chapter 10 10.1 Meiosis Meiosis I • The sexual life cycle in animals involves meiosis. • Meiosis produces gametes.

30. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Stages ofMeiosisI • Reduces the chromosome number by half through the separation of homologous chromosomes • Involves two consecutive cell divisions called meiosis I and meiosis II

31. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Meiosis I • Interphase • Chromosomes replicate. • Chromatin condenses. Interphase

32. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Meiosis I • Prophase I • Pairing of homologous chromosomes occurs. • Each chromosome consists of two chromatids. Prophase I • The nuclear envelope breaks down. • Spindles form.

33. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Meiosis I • Prophase I • Crossing over produces exchange of genetic information. • Crossing over—chromosomal segments are exchanged between a pair of homologous chromosomes.

34. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Meiosis I • Metaphase I • Chromosome centromeres attach to spindle fibers. Metaphase I • Homologous chromosomes line up at the equator.

35. Sexual Reproduction and Genetics • Homologous chromosomes separate and move to opposite poles of the cell. Chapter 10 10.1 Meiosis Meiosis I • Anaphase I Anaphase I

36. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Meiosis I • Telophase I • The spindles break down. Telophase I • Chromosomes uncoil and form two nuclei. • The cell divides.

37. Sexual Reproduction and Genetics • A second set of phases begins as the spindle apparatus forms and the chromosomes condense. Chapter 10 10.1 Meiosis Meiosis II • Prophase II Prophase II

38. Sexual Reproduction and Genetics • A haploid number of chromosomes line up at the equator. Chapter 10 10.1 Meiosis Meiosis II • Metaphase II Metaphase II

39. Sexual Reproduction and Genetics • The sister chromatids are pulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell. Chapter 10 10.1 Meiosis Meiosis II • Anaphase II Anaphase II

40. Sexual Reproduction and Genetics • The chromosomes reach the poles, and the nuclear membrane and nuclei reform. Chapter 10 10.1 Meiosis Meiosis II • Telophase II Telophase II

41. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Meiosis II • Cytokinesis results in four haploid cells, each with n number of chromosomes. Cytokinesis

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43. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis The Importance of Meiosis • Meiosis consists of two sets of divisions • Produces four haploid daughter cells that are not identical • Results in genetic variation

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45. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Meiosis Provides Variation • Depending on how the chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result. • Genetic variation also is produced during crossing over and during fertilization, when gametes randomly combine.

46. Sexual Reproduction and Genetics Chapter 10 10.1 Meiosis Sexual Reproduction v. Asexual Reproduction • Asexual reproduction • The organism inherits all of its chromosomes from a single parent. • The new individual is genetically identical to its parent. • Sexual reproduction • Beneficial genes multiply faster over time.