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Chapter 8: Cell Reproduction

0. Chapter 8: Cell Reproduction. Original slide set from: www.laney.edu/wp/laura_coronado/files/2011/08/SV Chap - 8 .ppt. WHAT CELL REPRODUCTION ACCOMPLISHES. Reproduction: May result in the birth of new organisms More commonly involves the production of new cells. Cell Division.

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Chapter 8: Cell Reproduction

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  1. 0 Chapter 8: Cell Reproduction Original slide set from: www.laney.edu/wp/laura_coronado/files/2011/08/SVChap-8.ppt

  2. WHAT CELL REPRODUCTION ACCOMPLISHES • Reproduction: • May result in the birth of new organisms • More commonly involves the production of new cells

  3. Cell Division • Cell division plays important roles in the lives of organisms. • Replaces damaged or lost cells • Permits growth • Allows for reproduction

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

  5. Asexual Reproduction • Single-celled organisms reproduce by simple cell division • There is no fertilization of an egg by a sperm • The parent and its offspring have identical genes.

  6. Asexual Reproduction Binary Fission Prokaryotic cells divide through a simple form of division calledBinary Fission 3 step process Single “naked” strand splits and forms a duplicate of itself. The two copies move to opposite sides of the cell Cell “pinches” into two new and identical cells called "daughter cells". (Cell wall then forms if applicable)

  7. Asexual Reproduction • Mitosis is the type of cell division responsible for: • Asexual reproduction • Growth and maintenance of multicellular organisms • Some multicellular organisms, such as sea stars, can grow new individuals from fragmented pieces. • Growing a new plant from a clipping

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

  9. Sexual Reproduction • Sexual reproduction requires fertilization of an egg by a sperm using a special type of cell division called meiosis. • Thus, sexually reproducing organisms use: • Meiosis for reproduction • Mitosis for growth and maintenance

  10. LM Chromosomes Figure 8.3

  11. Chromosomes • Chromosomes: • Are made of chromatin, a combination of DNA and protein molecules • Are not visible in a cell until cell division occurs • Before a parent cell splits into two, it duplicates its chromosomes

  12. 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

  13. Eukaryotic Cell Genetic Information • Most genes on chromosomes in cell nucleus • A few genes found in mitochondrial and chloroplast DNA • Each chromosome: one very long DNA molecule, typically with thousands of genes. • Histones are proteins used to package DNA. • Nucleosomes consist of DNA wound around histone molecules.

  14. DNA double helix Histones “Beads on a string” TEM Nucleosome Tight helical fiber Looped domains Duplicated chromosomes (sister chromatids) TEM Centromere Laura Coronado Bio 10 Chapter 8 Figure 8.4

  15. Chromosome (one long piece of DNA) Centromere Sister chromatids Duplicated chromosome Laura Coronado Bio 10 Chapter 8 Figure 8.UN2

  16. Chromosomes • Before a cell divides, it duplicates all of its chromosomes, resulting in two copies called sister chromatids. • Sister chromatids are joined together at a narrow “waist” called the centromere. • When the cell divides, the sister chromatids separate from each other. • Once separated, each chromatid is: • Considered a full-fledged chromosome • Identical to the original chromosome

  17. Chromosome distribution to daughter cells Chromosome duplication Sister chromatids Laura Coronado Bio 10 Chapter 8 Figure 8.5

  18. The Cell Cycle • A cell cycle is the orderly sequence of events that extend from the time a cell is first formed from a dividing parent cell to its own division into two cells. • The cell cycle consists of two distinct phases: • Interphase • The mitotic phase

  19. S phase (DNA synthesis; chromosome duplication) Interphase: metabolism and growth (90% of time) G1 G2 Mitotic (M) phase: cell division (10% of time) Cytokinesis (division of cytoplasm) Mitosis (division of nucleus) Laura Coronado Bio 10 Chapter 8 Figure 8.6

  20. Interphase

  21. Interphase • Most of a cell cycle is spent in interphase. • During interphase, a cell: • Performs its normal functions • Doubles everything in its cytoplasm • Grows in size Laura Coronado Bio 10 Chapter 8

  22. Interphase • Interphase • 3 Stages • G1 (Gap 1)Phase - Cell performs its normal function (cells which do not divide stay in this stage for their entire life span) • -cells grow and mature • S (Synthesis) Phase - Here the cell actively duplicates its DNA in preparation for division • G2 (Gap 2) Phase - Amount of cytoplasm (including organelles) increases in preparation for division. • Another possibility • G0 Phasecells do not prepare for cell division • Generally straight from G1 phase • Example: fully developed cells in Central Nervous System never divide again

  23. Mitosis

  24. Mitosis • 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

  25. Mitosis and Cytokinesis • Mitosis consists of four distinct phases: • (A) Prophase • (B) Metaphase • (C) Anaphase • (D) Telophase • Cytokinesis typically: • Occurs during telophase • Divides the cytoplasm • Is different in plant and animal cells

  26. 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

  27. Prophase • Chromosomes condense • Nuclear membrane breaks down • Centrioles migrate to opposite poles (in animal cells) • Microtubules attach to chromosomes and centrioles

  28. Prophase

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

  30. Metaphase • Chromosomes line up along the center of the cell

  31. Metaphase

  32. Anaphase • Microtubules shorten • Chromatids separate a pull to opposite sides

  33. Anaphase

  34. Telophase • Nuclear membrane forms around each set of chromosomes • Chromosomes unwind

  35. Cytokinesis • Cytoplasm split in two • Cell membrane separates the two daughter cells

  36. Telophase and Cytokinesis

  37. Animal cell mitosis

  38. SEM Cleavage furrow Cleavage furrow Contracting ring of microfilaments Daughter cells Figure 8.8a

  39. Plant Cell Mitosis • Plant cell mitosis is similar to animal cell mitosis BUT cytokinesis is different • In plant, fungi and algae cell, a cell plate forms in the middle of the cell to divide the two cells.

  40. Wall of parent cell Cell plate forming Daughter nucleus LM Vesicles containing cell wall material Cell plate Cell wall New cell wall Daughter cells Figure 8.8b

  41. Result of Mitosis • 2 daughter cells that are identical to each other and identical to the parent cell

  42. 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.

  43. What Is Cancer? • Cancer is a disease of the cell cycle. • Cancer cells do not respond normally to the cell cycle control system. • Cancer cells can form tumors, abnormally growing masses of body cells. • The spread of cancer cells beyond their original site of origin is metastasis. • Malignant tumors can: • Spread to other parts of the body • Interrupt normal body functions

  44. Lymph vessels Tumor Blood vessel Glandular tissue A tumor grows from a single cancer cell. Metastasis: Cancer cells spread through lymph and blood vessels to other parts of the body. Cancer cells invade neighboring tissue. Figure 8.9

  45. Cancer Treatment • Cancer treatment can involve: • Radiation therapy, which damages DNA and disrupts cell division • Chemotherapy, which uses drugs that disrupt cell division

  46. Cancer Prevention and Survival • Certain behaviors can decrease the risk of cancer: • Not smoking • Exercising adequately • Avoiding exposure to the sun • Eating a high-fiber, low-fat diet • Performing self-exams • Regularly visiting a doctor to identify tumors early

  47. Meiosis

  48. Homologous Chromosomes • Different individuals of a single species have the same number and types of chromosomes. • A human somatic cell: • Is a typical body cell • Has 46 chromosomes • A karyotype is an image that reveals an orderly arrangement of chromosomes. • Homologous chromosomes are matching pairs of chromosomes that can possess different versions of the same genes.

  49. LM Pair of homologous chromosomes Centromere Sister chromatids One duplicated chromosome Figure 8.11

  50. Human Chromosomes • Humans have: • Two different sex chromosomes, X and Y • Twenty-two pairs of matching chromosomes, called autosomes • Humans are diploid organisms in which: • Their somatic cells contain two sets of chromosomes • Their gametes are haploid, having only one set of chromosomes

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