Cell Growth and Division Biology Honors PDF

Cell Growth and Division Chapter 8 Biology Honors  I. Cell Growth – Some organisms reproduce asexually And their offspring are genetic copies of the parent and of each other – Other organisms reproduce sexually Creating a variety of offspring Cells arise only from preexisting...

Cell Growth and Division Chapter 8 Biology Honors  I. Cell Growth – Some organisms reproduce asexually And their offspring are genetic copies of the parent and of each other – Other organisms reproduce sexually Creating a variety of offspring Cells arise only from preexisting cells – Cell division is at the heart of the reproduction of cells and organisms  Prokaryotes reproduce by binary fission – Prokaryotic cells reproduce asexually by cell division Prokaryotic chromosomes Colorized TEM 32,500× Figure 8.3B Plasma membrane Prokaryotic Cell wall chromosome Duplication of the chromosome 1 and separation of the copies Continued elongation of the 2 cell and movement of the copies Division into 3 two daughter cells  Limits to Cell Growth - two reasons why cells divide rather than continue to grow 1. DNA “overload” - there are more demands for the DNA. 2. Exchanging materials – the cell has trouble moving enough nutrients and wastes across the cell membrane  THE EUKARYOTIC CELL CYCLE AND MITOSIS – A eukaryotic cell has many more genes than a prokaryotic cell They are grouped into multiple chromosomes in the nucleus. Individual chromosomes are visible under a light microscope only when the cell is in the process of dividing; otherwise, chromosomes are thin, loosely packed chromatin fibers too small to be seen.  – Before a cell starts dividing, the chromosomes replicate Sister chromatids Producing sister chromatids joined together at the centromere Centromer e TEM 36,000× Figure 8.3B  – Cell division involves the separation of sister chromatids And results in two Chromosome daughter cells, duplication each containing Sister Centromere chromatids a complete and identical set of chromosomes Chromosome distribution to daughter cells Figure 8.3B The cell cycle consists of two major phases -Interphase & Mitotic phase INTERPHASE G1 S (DNA synthesis) sis G2 k ine s yto si ito C M MIT PH OTIC AS E (M ) – During interphase Chromosomes duplicate and cell parts are made. – During the mitotic phase Duplicated chromosomes are evenly distributed into two daughter nuclei.  – The stages of cell division LM 250× INTERPHASE PROPHASE PROMETAPHASE Centrosomes Fragments Early mitotic Centrosome (with centriole pairs) of nuclear spindle Kinetochore Chromatin envelope Nucleolus Nuclear Plasma Chromosome, consisting Centromere Spindle envelope membrane ot two sister chromatids microtubules Figure 8.6 (Part 1)  METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Metaphase Cleavage Nucleolus plate furrow forming Daughter Nuclear Spindle chromosomes envelope forming Figure 8.6 (Part 2) Video: Animal Mitosis © 2018 Pearson Education, Inc. Cytokinesis differs for plant and animal cells – In animals Cytokinesis occurs by a constriction of Cleavage SEM 140× the cell (cleavage) furrow Cleavage furrow Contracting ring of microfilaments Daughter cells Figure 8.6A  Cell plate Wall of Daughter – In plants forming parent cell nucleus A membranous cell plate splits the cell in two TEM 7,500× Cell wall New cell wall Vesicles containing Cell plate Daughter cells cell wall material Figure 8.6B  In laboratory cultures, most normal cells divide only when attached to a surface (anchorage dependence). – The cultured cells continue dividing until they touch one another. (density-dependent inhibition) – Most animal cells divide only when stimulated by growth factors, and some do not divide at all. Anchorage Single layer of cells Removal of cells Restoration of single layer by cell division Cancer cells forming clump of overlapping cells Growth factors Cultured cells suspended in liquid The addition of growth factor Cells divide in Cells fail presence of to divide growth factor A set of proteins within the cell controls the cell cycle. Signals affecting critical checkpoints in the cell cycle determine whether a cell will go through the complete cycle and divide. The binding of growth factors to specific receptors on the plasma membrane is usually necessary for cell division. The cell cycle consists of four phases: –G1 (First Gap Phase) –S Phase –G2 (Second Gap Phase) –M Phase  *G 1 phase –increases in size –synthesizes new proteins and organelles *S phase - chromosomes are replicated - DNA synthesis takes place *G 2 phase - organelles and molecules required for cell division are produced  G1 checkpoint G0 Control system G1 S M G2 M checkpoint G2 checkpoint  G1 checkpoint G0 S G1 Control system M G2 M checkpoint G2 checkpoint Mitosis  Growing out of control, cancer cells produces malignant tumors – Cancer cells divide excessively to form masses called tumors https://www.youtube.com/watch?v=IeUANxFVXKc  Lymph vessels Blood vessel Tumo r Tumor in Glandular another tissue part of the body Tumor Invasion Metastasis growth  MEIOSIS AND CROSSING OVER Chromosomes are matched in homologous pairs – The somatic (body) cells of each species Contain a specific number of chromosomes – For example human cells have 46 Making up 23 pairs of homologous chromosomes  – The chromosomes of a homologous pair Carry genes for the same characteristics at the same place, or locus Chromosom es Centromer e Figure 8.11 Sister chromatids  Gametes have a single set of chromosomes – Cells with two sets of chromosomes Are said to be diploid – Gametes, eggs and sperm, are haploid With a single set of chromosomes – The first division, meiosis I Starts with synapsis, the pairing of homologous chromosomes – In crossing over Homologous chromosomes exchange corresponding segments – Meiosis I separates each homologous pair And produce two daughter cells, each with one set of chromosomes – Meiosis II is essentially the same as mitosis The sister chromatids of each chromosome separate The result is a total of four haploid cells  – The stages of meiosis MEIOSIS I: Homologous chromosomes separate INTERPHASE PROPHASE I METAPHASE I ANAPHASE I Centrosomes Microtubules Sister chromatids Sites of crossing over Metaphase (with centriole attached to remain attached plate pairs) kinetochore Spindle Nuclear Sister Centromere Homologous envelope Chromatin chromatids Tetrad (with kinetochore) chromosomes separate Figure 8.14 (Part 1)  MEIOSIS II: Sister chromatids separate TELOPHASE I TELOPHASE II PROPHASE II METAPHASE II ANAPHASE II AND CYTOKINESIS AND CYTOKINESIS Cleavage furrow Sister chromatids Haploid daughter cells separate forming Figure 8.14 (Part 2) Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring – Each chromosome of a homologous pair differs at many points from the other member of the pair  – Random arrangements of chromosome pairs at metaphase I of meiosis Lead to many different combinations of chromosomes in eggs and sperm Possibility Possibility 1 Two equally 2 probable arrangements of chromosomes at metaphase I Metaphase II Gamete s Figure 8.16 Combination 1 Combination 2 Combination 3 Combination 4  Homologous chromosomes carry different versions of genes – The differences between homologous chromosomes is they can bear different versions of a gene at corresponding loci Brown coat (C); black eyes (E) White coat (C); pink eyes (e) Coat-color Eye-color genes genes Brown Black C E C E C E Meiosis c e c e White Pink c e Tetrad in parent cell (homologous pair of Chromosomes of duplicated chromosomes) the four gametes Figure 8.17B Figure 8.17A  Crossing over further increases genetic variability – Genetic recombination, results from crossing over during prophase I of meiosis. TEM 2,200× Chiasma Tetrad Centromere Figure 8.18A  – How crossing Coat-color genes C Eye-color genes E Tetrad (homologous over leads to c e pair of chromosomes in synapsis) genetic variation 1 Breakage of homologous chromatids C E c e 2 Joining of homologous chromatids C E Chiasma c e Separation of homologous 3 chromosomes at anaphase I C E C e c E c e Separation of chromatids at 4 anaphase II and completion of meiosis C E Parental type of chromosome C e Recombinant chromosome c E Recombinant chromosome c e Parental type of chromosome Gametes of four genetic types Figure 8.18B A karyotype is a photographic inventory of an individual’s chromosomes An ordered arrangement of a cell’s chromosomes Human male karyotype Human female karyotype – Abnormal chromosome count is a result of nondisjunction The failure of homologous pairs to separate during meiosis I The failure of sister chromatids to separate during meiosis II Nondisjunction in meiosis I Normal meiosis I Normal Nondisjunction meiosis II in meiosis II Gametes Gametes n+1 n −1 n n n+1 n+1 n −1 n −1 Number of chromosomes Number of chromosomes Figure 8.21B Figure 8.21A  Egg cell n+ 1 Zygot Sperm e cell 2n + n 1 (normal) Figure 8.21C Normal and Cancer Karyotypes  – Deletions, duplications, inversions, and translocations Reciprocal translocation Deletion Nonhomologous chromosomes Figure 8.23B Chromosome 9 Duplication Homologous chromosomes Reciprocal Chromosome 22 translocation Inversion “Philadelphia chromosome” Activated cancer-causing gene Figure 8.23C Figure 8.23A