Chapter 8 Cellular Reproduction: Cells from Cells

1. Chapter 8 Cellular Reproduction: Cells from Cells General Biology CM Lamberty

2. Biology and Society • Rain Forest Rescue • Pollination of near extinction • Endangered species of plants that normally reproduce sexually can by propagated by asexual reproduction. • Cell division is at the heart of organismal reproduction, whether by sexual or asexual means

3. Figure 8.00a

4. What Cellular Reproduction Accomplishes • Reproduction: • When a cell undergoes reproduction, or celldivision, • Before a parent cell splits into two • During cell division, each daughter cell receives one set of chromosomes.

5. FUNCTIONS OF CELL DIVISION Cell Replacement Growth via Cell Division Colorized TEM LM Human kidney cell Early human embryo Figure 8.1a

6. FUNCTIONS OF CELL DIVISION Asexual Reproduction LM Sea stars African Violet Amoeba Figure 8.1b

7. What Cellular Reproduction Accomplishes • In asexual reproduction: • Some multicellular organisms, such as sea stars, can grow new individuals from fragmented pieces. • Growing a new plant from a clipping is another example of asexual reproduction. • In asexual reproduction, • Mitosis is the type of cell division responsible for: • Sexual reproduction requires fertilization of an egg by a sperm using a special type of cell division called meisois

8. Cell Cycle and Mitosis • In a eukaryotic cell: • Most genes are located on chromosomes in the cell nucleus • A few genes are found in DNA in mitochondria and chloroplasts

9. Eukaryotic Chromosomes • Each eukaryotic chromosome contains one very long DNA molecule, typically bearing 1000s of genes • The number of chromosomes in a eukaryotic cell depends on the species

10. Number of chromosomes in body cells Species Indian muntjac deer 6 Koala 16 Opossum 22 Giraffe 30 40 Mouse 46 Human Duck-billed platypus 54 60 Buffalo Dog 78 102 Red viscacha rat Figure 8.2

11. Eukaryotic Chromosomes • Chromosomes • Are made of chromatin, a combination of DNA and protein molecules • Are not visible in a cell until cell divisions occurs Chromosomes

12. Eukaryotic Chromosomes • THE DNA in a cell is packed into an elaborate, multilevel system of coiling and folding

13. DNA double helix Histones “Beads on a string” TEM Nucleosome Tight helical fiber Looped domains Duplicated chromosomes (sister chromatids) TEM Centromere Figure 8.4

14. Eukaryotic Chromosomes • Before a cell divides, it duplicates all of its chromosomes, resulting • Sister chromatids are joined together • When the cell divides, • Once separated, each chromatid is

15. Chromosome distribution to daughter cells Chromosome duplication Sister chromatids Figure 8.5

16. The Cell Cycle • A cell cycle is the orderly sequence of events • The cell cycle consists of two district phases: • Most of the cell cycle is spent in interphase • During interphase, a cell:

18. The Cell Cycle • The mitotic (M) phase includes two overlapping processes: • Mitosis, in which the nucleus and its contents divide evenly into two daughter nuclei • Cytokinesis, in which the cytoplasm is divided in two

19. Mitosis and Cytokinesis • During mitosis the mitotic spindle, • Spindle microtubules grow from • Mitosis consists of four distinct phases:

20. INTERPHASE PROPHASE Fragments of nuclear envelope Early mitotic spindle Centrosomes (with centriole pairs) Centrosome Chromatin Centromere Chromosome, consisting of two sister chromatids Nuclear envelope Spindle microtubules Plasma membrane LM Figure 8.7.a

21. METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Cleavage furrow Nuclear envelope forming Daughter chromosomes Spindle Figure 8.7b

22. Mitosis and Cytokinesis • Cytokinesis typically:

25. Cancer Cells: growing out of control • Normal plant and animal cells have a cell cycle control system that consists of specialized proteins, which send “stop” and “go-ahead” signals at certain key points during the cell cycle. • What is cancer? • Cancer cells can form tumors • The spread of cancer cells beyond their original site of origin is • Malignant tumors can • A person with a malignant tumor is said to have cancer

26. Cancer Cells: growing out of control

27. Cancer Treatment • Cancer treatment can involve:

28. Cancer Prevention and Survival • Certain behaviors can decrease the risk of cancer:

29. Meiosis, the Basis of Sexual Reproduction • Sexual Reproduction: • Uses meiosis • Uses fertilization • Produces offspring that contain a unique combination of genes from the parents.

30. Homologous Chromosomes • Different individuals of a single • A human somatic cell • A karyotype is an image • Homologous chromosomes are • Humans have:

32. Gametes and the Life Cycle of Sexual Organisms • The life cycle of a multicellular organism is the sequence of stages • Humans are diploid organisms in which • In humans a haploid sperm fuses with a haploid egg during • Sexual life cycles involve an alternation • Meiosis produces

37. The Process of Meiosis • In meiosis

40. Review: Comparing Mitosis and Meiosis • In mitosis and meiosis, the chromosomes duplicate only once, during the preceding interphase. • The number of cell divisions varies: • All the events unique to meiosis occur during meiosis I

42. The Origin of Genetic Variation • Offspring of sexual reproduction • Independent Assortment of chromosomes • When aligned during metaphase I of meiosis, • Every chromosome pair orients • For any species the to total number of chromosome combinations that can appear in the gametes due to independent assortment is • 2n where n is the haploid number

46. Random Fertilization • A human egg cell is fertilized randomly by one sperm,

47. Crossing Over • In crossing over: • Genetic recombination,