Why do cells reproduce?

Transcription

1 Outline Cell Reproduction 1. Overview of Cell Reproduction 2. Cell Reproduction in Prokaryotes 3. Cell Reproduction in Eukaryotes 1. Chromosomes 2. Cell Cycle 3. Mitosis and Cytokinesis Examples of Cell Numbers Human Body 50,000,000,000,000 cells Red blood cells 25,000,000,000 RBCs replaced every day 1,400,000,000 Intestinal Epithelium Cells Last 1.5 days 4. Sexual Life Cycle & Meiosis Why do cells reproduce? 1. Single celled organisms reproduction 2. Multicellular organisms 1. Growth increase number of cells 2. Maintenance of existing cells 3. Repair of damaged cells Prokaryotic chromosome Figure 8.3A Binary fission of a prokaryotic cell 1 2 Plasma membrane Cell wall Duplication of chromosome and separation of copies Cell elongation and movement of DNA copies 3 Division into two daughter cells Protein Ring 3 Genome Size Varies Eukaryote Chromosome Structure Chromatids Centromere DNA Histone Protein Chromatids Centromere 1

2 Chromosome Structure Karyotype of Human Chromosomes Chromosome Replication Chromosome Chromosome Numbers G 1 Cytokinesis Mitosis INTERPHASE G 2 Reproductive Phase M Chromosomes condense and chromatids separate S Cell Cycle of Eukaryotes INTERPHASE G1 - Primary Growth S - DNA Synthesis G2 Mitochondria replicate Chromosomes condense C Cytoplasm separates Cytokinesis Mitosis in Eukaryotes Mitosis Separation of Chromosomes Division of Nucleus Stages of Mitosis Prophase Metaphase Anaphase Telophase Figure 8.6 The stages of cell division (part 1) LM 250 INTERPHASE PROPHASE PROMETAPHASE Centrosomes Mitotic Centrosome Nuclear Chromatin spindle Envelope Fragments Kinetochore Nucleus Plasma membrane Chromatids Centromere Spindle Microtubules 2

3 Figure 8.6 The stages of cell division (part 2) Figure 8.7A Cytokinesis in an animal cell METAPHASE ANAPHASE TELOPHASE Cleavage furrow SEM 140 Spindle Cleavage furrow Contracting ring of microfilaments Metaphase plate Chromatids Separating Nuclear envelope forming Daughter cells Figure 8.7B Cell plate formation in a plant cell Cell plate Mitosis in Plant Cells Daughter nucleus TEM 7,500 Cell wall New cell wall Vesicles containing cell wall material Cell plate Daughter cells Controlling the Cell Cycle Controlling the Cell Cycle G 0 G 1 checkpoint G 1 Control system S M G 2 M checkpoint G 2 checkpoint Figure 8.9A 3

4 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Receptor protein Controlling the Cell Cycle Growth factor Signal transduction pathway Relay proteins Kinases G 1 checkpoint G 1 Plasma membrane M Cyclins & Cyclin- Dependent Control system G 2 S Signal transduction pathway Cytoplasm Ras protein Src kinase Rb protein Nucleus p53 protein Cyclins & Cyclin- Dependent Kinases PROTO-ONCOGENES Growth factor receptor: more per cell in many breast cancers. Ras protein: activated by mutations in 20 30% of all cancers. Src kinase: activated by mutations in 2 5% of all cancers. TUMOR-SUPPRESSOR GENES Rb protein: mutated in 40% of all cancers. p53 protein: Cell cycle checkpoints mutated in 50% of all cancers. Figure 8.9B 20 Tumors Interfering with Cell Division Radiation Chemotherapy Tumor Lymph vessels Blood vessel Single cancer cell. Invade Neighboring Tissue Metastasize Periwinkle - Vinblastin Figure 8.10 Pacific Yew - Taxol END END Mitosis Mitosis Meiosis 4

5 Meiosis Learning Goals Unnumbered Figure p.149 Haploid gametes (n = 23) 1. Understand the differences between homologous and sister chromatids. n Egg cell 2. Distinguish between 1. autosomes and sex. 2. between somatic cells and reproductive cells 3. diploid cells and haploid cells. 3. Describe and recognize the events of Meiosis 4. Describe similarities & differences between mitosis and meiosis. 5. Explain how meiosis contributes to genetic variation in sexually reproducing organisms. Meiosis Multicellular diploid adults (2n = 46) Sperm cell HUMAN LIFE CYCLE n Diploid zygote (2n = 46) Fertilization 2n Mitosis and development Karyotype Diploid Organisms have Chromosomes Chromosomes Centromere Sister chromatids Figure 8.17A Differing genetic information on homologous Pair Coat-color genes Brown C c White Eye-color genes Black E e Pink Meiosis I Prophase I Metaphase I Anaphase I Telophase I Stages of Meiosis Meiosis II Prophase II Metaphase II Anaphase II Telophase II 5

6 Meiosis I - Prophase 1. Chromosomes condense 2. Nuclear envelope dissolves 3. Centrioles move apart 4. Spindle apparatus forms 5. Synapsis - pair up Meiosis I: Prophase: Synapsis and Crossover Synapsis Crossover Chromosomes after crossover Animation Meiosis I - Metaphase 1. align in an equatorial plane Meiosis I - Anaphase 1. separate 2. Reduction division of where 2N 1N Meiosis I - Telophase 1. Chromosomes decondense 2. Nuclear membrane forms 3. Spindle apparatus disappears 4. Cytokinesis Two haploid daughter cells form Figure 8.14 The stages of meiosis MEIOSIS I: separate PROPHASE I METAPHASE I ANAPHASE I INTERPHASE Centrosomes Crossing over Sister chromatids Spindle Haploid Daughter Cells Chromatin Sister chromatids pair up separate 6

7 Figure 8.14 The stages of meiosis Meiosis - Summary TELOPHASE I AND CYTOKINESIS MEIOSIS II: Chromatids separate PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II AND CYTOKINESIS Sister chromatids separate Haploid daughter cells form Figure 8.15 Comparison of mitosis and meiosis MITOSIS MEIOSIS Figure 8.19 Preparation of a karyotype from a blood sample Prophase Duplicated chromosome (two sister chromatids) Parent cell (before chromosome replication) Chromosome Chromosome replication replication 2n = 4 MEIOSIS I Prophase I Tetrad formed by synapsis of homologous Blood culture Centrifuge Hypotonic solution Fixative White blood cells Stain Metaphase Chromosomes align at the metaphase plate Tetrads align at the metaphase plate Metaphase I Anaphase Telophase 2n Sister chromatids separate during anaphase 2n Daughter cells of mitosis separate during anaphase I; sister chromatids remain together No further chromosomal replication; sister chromatids separate during anaphase II Anaphase I Telophase I Haploid n = 2 Daughter cells of meiosis I MEIOSIS II n n n n Daughter cells of meiosis II 4 5 2,600 Figure 8.21A Nondisjunction in meiosis I Figure 8.21B Nondisjunction in Meiosis II Nondisjunction in meiosis I Normal meiosis I Normal meiosis II Nondisjunction in meiosis II Gametes n + 1 n + 1 n 1 n 1 Number of Gametes n + 1 n 1 n n Number of 7

8 Figure 8.21C Fertilization after nondisjunction in the mother Figure 8.20B A child with Down syndrome = Trisomy Most common birth defect 2. 1 in 700 Egg cell n Physical features Round face Flattened nose bridge Short stature Heart defects n (normal) Zygote 2n Susceptibility to infections Sperm cell Figure 8.20C Maternal age and incidence of Down syndrome Infants with Down syndrome (per 1,000 births) Age of mother Figure 8.22A A man with Klinefelter syndrome (XXY) Poor beard growth Breast Development Under-developed testes Gamete from Male Parent XY XXY Gamete from Female Parent X Figure 8.22B A woman with Turner syndrome (XO) Figure 8.16 Independent Assortment of at metaphase I Web of skin Constriction of aorta Gamete from Male Parent O Gamete from Female Parent X Possibility 1 Possibility 2 Metaphase I Arrangements Poor breast development XO Metaphase II Underdeveloped ovaries Gametes Combination 1 Combination 2 Combination 3 Combination 4 8

9 END Meiosis 9