Where were we and where are we going next?

1. Cellular Reproduction Chapter 9 Where were we and where are we going next?

2. Cellular Reproduction Chapter 9 9.1 Cellular Growth • Overview of Cell Division – Mitosis and Meiosis • Asexual and Sexual Reproduction • Diploid vs. Haploid

3. Cellular Reproduction Chapter 9 Mitosis Meiosis Sexual Reproduction Passing of genetic traits Sex chromosomes aka gametes (X and Y) Haploid (n) Crossing Over Produces genetically different daughter cells • Asexual reproduction • Growth and repair • Somatic chromosomes (body chromosomes) • Diploid (2n) • No Crossing Over • Produces identical daughter cells

4. Cellular Reproduction Chapter 9 Asexual Reproduction Sexual Reproduction Genetic diversity Production of gametes to fuse with another gamete (XX or XY) Produces genetically different offspring Ability to adapt to change in environments • No genetic diversity • Can refer to the production of offspring from one parent (binary fission in bacteria) • Produces two identical offspring • Susceptible to diseases and changing environments

5. Cellular Reproduction Chapter 9 Haploid Diploid Refers to two sets of chromosomes (2n) Humans have ___ chromsomes Diploid would be ____ Fruit fly have ___ chromosomes Diploid would be ____ • Refers to one set of chromosomes (n) • Humans have ___ chromosomes • Haploid would be ____ • Fruit fly have ___ chromosomes • Haploid would be ____

6. Cellular Reproduction Chapter 9 What are chromosomes? • Chromosomes are rod-shaped structures made up of DNA and proteins. • Two chromatids make up a chromosome • Centromeres are attachment points for two chromatids and hold them together • Chromatin are less tightly coiled DNA-protein complex used to form chromosomes

7. Cellular Reproduction chromatid centromere Condensed, duplicated chromosome Chapter 9 Confused yet?

8. Cellular Reproduction Chapter 9 9.1 Cellular Growth The Cell Cycle • The main purpose of cell division – to grow and heal certain injuries. • Cells reproduce by a cycle of growing and dividing called the cell cycle.

9. Cellular Reproduction Chapter 9 Cell cycle in three different stages

10. 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.

11. Cellular Reproduction Chapter 9 9.1 Cellular Growth The Stages of Interphase • The first stage of interphase, Gap1 • The cell is growing, carrying out normal cell functions, and preparing to replicate DNA.

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

13. Cellular Reproduction Chapter 9 9.1 Cellular Growth The Third Stage of Interphase, Gap2 • The cell continues to grow and prepares for the division of its nucleus.

14. 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. • Two chromatids become one chromosome. • Spindle fibers form in the cytoplasm.

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

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

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

18. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis • The sister chromatids now become separate chromosomes.

19. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis Telophase • Two new nuclear membranes begin to form and the nucleoli reappear. • The spindle apparatus disassembles. • The pinching between the newly formed cells (called a cleavage furrow) is an indication of telophase.

20. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis

21. 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.

22. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis • Division of two IDENTICAL daughter cells with the same amount of chromosomes (DNA).

23. 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.

24. 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.

25. Cellular Reproduction Chapter 9 9.3 Cell Cycle Regulation Causes of Cancer • Mutations that cause problems in the regulation of cell growth and division • Various environmental factors can affect the occurrence of cancer cells.

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 Homologous chromosomes • 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

42. 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

43. 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.

44. 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.