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08 Lecture Ppt 08 Lecture Ppt Presentation Transcript

  • Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 8 Cell Division and Reproduction
  • Cell Division Ensures the Passage of Genetic Information 8-
  • 8.1 Cell division is involved in both asexual and sexual reproduction
    • Somatic cells - body cells make up most of the organism
      • Asexual reproduction - increase in number of somatic cells or the number unicellular organisms
    • Germ cells - found only in testes and ovaries, they produce sperm or eggs
      • Sexual reproduction – requires the production of eggs and sperm
    8-
  • 8.2 Prokaryotes reproduce asexually
    • In bacteria and archaea, reproduction consists of duplicating the single chromosome, located in the nucleoid, and distributing a copy to each daughter cell
    8-
  • Figure 8.2 Prokaryotes use binary fission to reproduce 8-
  • Somatic Cells Have a Cell Cycle and Undergo Mitosis and Cytokinesis 8-
  • 8.3 The eukaryotic cell cycle is a set series of events
    • Interphase - the time when a cell performs its usual functions
    • Figure 8.3A Stages of the cell cycle.
    8-
  • M (Mitotic) Stage
    • Cell division occurs during the M stage and encompasses both division of the nucleus and division of the cytoplasm
      • Mitosis - nuclear division in the cell cycle
      • Cytokinesis - division of the cytoplasm
    8-
  • Figure 8.3B Cytokinesis is a noticeable part of the cell cycle 8-
  • 8.4 Eukaryotic chromosomes are visible during cell division
    • When a eukaryotic cell is not undergoing division, the DNA within a chromosome is a mass of thin threads called chromatin
      • Before nuclear division chromatin condenses,
      • 2 identical chromatids are sister chromatids
    8-
  • Figure 8.4A A condensed duplicated chromosome 8-
  • Somatic Cells Are Diploid (2n)
    • Diploid (2n) - includes two chromosomes of each kind
    • During mitosis, a 2n nucleus divides to produce daughter nuclei that are also 2n
      • A dividing cell is called the parent cell and the new cells are called the daughter cells
    8-
  • Gametes Are Haploid (n)
    • Haploid (n) number of chromosomes, contains only one chromosome of each kind
      • Half the diploid number
    • Figure 8.4B When sister chromatids separate, each daughter nucleus gets a chromosome
    8-
  • 8.5 Mitosis maintains the chromosome number
    • Before mitosis, DNA has replicated, each double helix is in a chromatid and the chromosomes consist of sister chromatids attached at a centromere
      • The centrosome - the microtubule-organizing center of the cell divides before mitosis
      • Spindle fibers separate the sister chromatids of the duplicated chromosomes
    8-
  • 8- Figure 8.5 Phases of mitosis in animal cells and plant cells
  • Figure 8.5 Phases of mitosis in animal cells and plant cells 8-
  • 8.6 Cytokinesis divides the cytoplasm
    • Cytokinesis follows mitosis in most cells
    • Cytokinesis in plant cells occurs by a process different than in animal cells
      • Cell plate - newly formed plasma membrane that expands outward
    8-
  • Figure 8.6A Cytokinesis in an animal cell 8-
  • Figure 8.6B Cytokinesis in plant cells 8-
  • Cancer Is Uncontrolled Cell Division 8-
  • 8.7 Cell cycle control occurs at checkpoints
    • The cell cycle has checkpoints that can delay the cell cycle until all is well
      • Apoptosis - programmed cell death
    8-
  • Figure 8.7 Cell cycle checkpoints 8-
  • 8.8 Signals affect the cell cycle control system
    • Signaling molecules stimulate or inhibit
    • Kinases remove phosphate from ATP and add it to another molecule
    • Cyclins combine with kinases
    • Control system for cell division control whether kinases and cyclins are present
    8-
  • Figure 8.8A Internal signals of the cell cycle are kinases and cyclins 8-
  • Figure 8.8B A cell-signaling pathway activates the control system to produce kinases and cyclins 8-
  • Cell Cycle Inhibition
    • Contact Inhibition - In a culture, cells divide until they line a container in a sheet and then stop dividing
    • Cells “remember” number of divisions
    • Telomere - repeating DNA base sequence
      • Each time a cell divides some portion of a telomere is lost
      • When telomeres become too short, chromosomes fuse and do not duplicate
    8-
  • 8.9 Cancer cells have abnormal characteristics
    • A mutation (a DNA change) causes a cell to divide uncontrollably or ignore apoptosis
      • Carcinogenesis - development of cancer
    • Characteristics of cancer cells
      • Lack differentiation
      • Have abnormal nuclei
      • Form tumors
      • Metastasis - establishing new tumors
      • Angiogenesis - formation of new blood vessels
    8-
  • Figure 8.9 Development of breast cancer 8-
  • APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 8.10 Protective behaviors and diet help prevent cancer
    • Behaviors that help prevent cancer
      • Don’t smoke
      • Use sunscreen
      • Avoid radiation
      • Be tested for cancer
      • Be aware of occupational hazards
      • Carefully consider hormone therapy
    • Dietary guidelines to reduce cancer risk
      • Increase consumption of foods rich in vitamins A and C
      • Limit consumption of salt-cured, smoked, or nitrite-cured foods
      • Include vegetables from the cabbage family
      • Be moderate in the consumption of alcohol
      • Maintain a healthy weight
    8-
  • Meiosis Produces Cells That Become the Gametes in Animals and Spores in Other Organisms 8-
  • 8.11 Homologous chromosomes separate during meiosis
    • Karyotype - picture of chromosomes in numbered pairs called homologous chromosomes or homologues
      • X and Y chromosomes are the sex chromosomes because they contain the genes that determine gender
        • Autosomes - all the pairs of chromosomes except the sex chromosomes
    8-
  • Figure 8.11 A karyotype shows that the chromosomes occur as pairs 8-
  • Meiosis
    • Occurs during the production of the sperm and egg
    • Requires two divisions
      • Meiosis I - the chromosomes of each homologous pair separate
      • Meiosis II - the sister chromatids of each duplicated chromosome separate
    8-
  • 8-
  • 8.12 Synapsis and crossing-over occur during meiosis I
    • Synapsis - homologous chromosomes come together and line up side by side forming a tetrad
    • Crossing-over - during synapsis, nonsister chromatids exchange genetic material
    8-
  • Figure 8.12A Synapsis of homologues 8-
  • Figure 8.12B Crossing-over of nonsister chromatids 8-
  • 8.13 Sexual reproduction increases genetic variation
    • Fertilization , the union of a male and a female gamete, enhances genetic variation
      • Sexual reproduction brings about genetic variation, and some offspring may have a better chance of survival and reproductive success than others
    8-
  • Figure 8.13 Independent assortment increases genetic variation 8-
  • 8.14 Meiosis requires two division cycles
    • Prophase, metaphase, anaphase, and telophase occur during both meiosis I and meiosis II
      • No replication of DNA occurs during a period called interkinesis between meiosis I and II
    8-
  • Figure 8.14A Phases of meiosis I 8-
  • Figure 8.14A Phases of meiosis I 8-
  • Figure 8.14B Phases of meiosis II 8-
  • Figure 8.14B Phases of meiosis II 8-
  • 8.15 The life cycle of most multicellular organisms includes both mitosis and meiosis
    • Life cycle - in sexually reproducing organisms, all the reproductive events from one generation to the next
      • Spermatogenesis in males, occurs in the testes and produces sperm
      • Oogenesis in females, occurs in the ovaries and produces eggs
    • Zygote - product of the sperm and egg joining during fertilization, has homologous pairs of chromosomes
    8-
  • Figure 8.15A Life cycle of humans 8-
    • Figure 8.15B Life cycle of plants Figure 8.15C Life cycle of algae
    8-
  • 8.16 Meiosis can be compared to mitosis 8-
  • Chromosomal Abnormalities Can Be Inherited 8-
  • 8.17 An abnormal chromosome number is sometimes traceable to nondisjunction
    • Polyploidy - a eukaryote has three or more complete sets of chromosomes
    • Aneuploidy - an organism has more or less than the normal number of chromosomes
      • Monosomy only one of a type of chromosome
      • Trisomy three of a type of chromosome
    • Nondisjunction - in meiosis I homologues do not separate and both go into the same daughter cell, or in meiosis II sister chromatids fail to separate and both daughter chromosomes go to the same gamete
    8-
  • Figure 8.17A Nondisjunction of chromosomes during meiosis I of oogenesis, followed by fertilization with normal sperm 8-
  • Figure 8.17B Nondisjunction of chromosomes during meiosis II of oogenesis, followed by fertilization with normal sperm 8-
  • 8.18 Abnormal chromosome numbers cause syndromes
    • Trisomy 21 (Down Syndrome)
      • Over 90% of individuals with Down syndrome have three copies of chromosome 21
    • Abnormal Sex Chromosome Inheritance
      • Turner syndrome females are born with only a single X chromosome
      • A male with Klinefelter syndrome has two or more X chromosomes in addition to a Y chromosome
    8-
  • 8.19 Abnormal chromosome structure also causes syndromes
    • Various agents in the environment, such as radiation, certain organic chemicals, or viruses, can cause chromosomes to break
      • Deletion - an end of a chromosome breaks off or two simultaneous breaks lead to the loss of an internal segment
      • Duplication - the presence of a particular chromosome segment more than once in the same chromosome
      • Inversion - a segment of a chromosome is turned 180 degrees
      • Translocation - the movement of a chromosome segment from one chromosome to another nonhomologous chromosome
    8-
  • Figure 8.19 Types of chromosomal mutations 8-
  • Connecting the Concepts: Chapter 8
    • All cells receive DNA from preexisting cells through the process of cell division
      • Mitosis is part of the cell cycle, and there are negative consequences if the cell cycle comes out of synchronization
      • Meiosis is part of the production of gametes, which have half the number of chromosomes as the parent cell
    • Sexual reproduction increases genetic variability
    8-