Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Ch. 5.2- Mitosis & Cytokinesis Mitosis “The Movie” Phases of the Cell Cycle • The cell cycle consists of ▫ Interphase – normal cell activity ▫ The mitotic phase – cell division Functions of Cell Division 100 µm (a) Reproduction. An amoeba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism (LM). 200 µm 20 µm (b) Growth and development. (c) Tissue renewal. These dividing This micrograph shows a bone marrow cells (arrow) will sand dollar embryo shortly after give rise to new blood cells (LM). the fertilized egg divided, forming two cells (LM). Chromosome • = one long continuous thread of DNA that consists of numerous genes & regulatory info. ▫ Your body cells have 46 chromosomes 23 from Mom & 23 from Dad • DNA wraps around proteins (histones) to keep it condensed and organized Chromosomes • Chromatins becomes more condensed as a cell goes into mitosis • Chromatid= one half of the duplicated chromosome ▫ 2 chromatids= sister chromatids ▫ The centromere holds the sister chromatids together • Telomers= are at the ends of DNA molecules & protect the genes from damage Mitosis • 4 phases of mitosis • Occurs in body cells resulting in two genetically identical nuclei • After mitosis, cytokinesis (splitting of cytoplasm) occurs Prophase • • • • Chromatid condenses Nuclear envelope breaks down Nucleolus disappears Centrosomes and centrioles migrate to opposite ends of the cell • Spindle fibers start to grow PROPHASE Aster Early mitotic Centromere spindle Chromosome, consisting of two sister chromatids Metaphase • Spindle fibers attach to each chromosome • Chromosomes align along the cell equator (metaphase plate) Spindle METAPHASE Metaphase plate Centrosome at one spindle pole Anaphase • Sister chromatids separate • Spindle fibers shorten which pulls sister chromatids away from each other & towards opposite ends of the cell ANAPHASE Daughter chromosomes Telophase • Complete set of identical chromosomes are at each pole of the cell • Nuclear membrane starts to form • Chromosomes begin to uncoil • Spindle fibers fall apart TELOPHASE AND CYTOKINESIS Cleavage furrow Nuclear envelope forming Nucleolus forming Cytokinesis • Cytoplasm divides into two cells and completes a full stage of the cell cyle • Different in plant & animal cells ▫ Animal cells- the membrane furrows ▫ Plant cells- a cell plate forms since the cell wall is too rigid for the cell to furrow (or pinch together) Cleavage furrow Contractile ring of microfilaments 100 µm Vesicles forming cell plate Wall of patent cell 1 µm Cell plate New cell wall Daughter cells Daughter cells (a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (SEM)