Chapter 8 The Cellular Basis of Reproduction and Inheritance 8 1 Cell division plays many important role in the lives of organisms Cell division cell undergoes reproduction to produce two daughter cells that are identical to the parent cell o Before splitting the parent cell must duplicate its chromosomes contains DNA A set of duplicated chromosomes are given to the daughter cells Asexual reproduction the creation of identical offspring from one parent cell o Prokaryotes and eukaryotic yeast cells generally use this form of reproduction o Several multicellular organisms can use it as well Mitosis involved in asexual reproduction and multicellular organism maintenance Sexual reproduction the creation of offspring from two parent cells o It requires fertilization of a sperm and egg gametes o Gametes only contain half the chromosomes necessary to create offspring o This type brings about a large variety in offspring Meiosis development of egg and sperm cells 8 2 Prokaryotes reproduce by binary fission Binary fission dividing in half o Reproduction of prokaryotes like bacteria and archaea o Steps Chromosomes duplicate and move to opposite sides of the cell Cell grows longer After the chromosomes are completely duplicated and the cell is twice its original size the plasma membrane grows inward and the cell wall grows to finish the division process 8 3 The large complex chromosomes of eukaryotes duplicate with each cell division Almost all genes are found in the nucleus of the cell o Exception mitochondria have their own DNA and in plants chloroplast made their own as well Chromatin DNA stretched out in its loose state o Fibers composed of roughly the same amounts of DNA and protein molecules o Too thin to be seen by microscope o Right before cell division chromatin coil together to maximize surface area for duplication Chromosomes vary by species o Examples Humans have 46 Dogs have 78 o Sister chromatin two copies of a DNA molecule Joined together by centromeres at the waist Called chromosomes after separation One goes to each daughter cell 8 4 The cell cycle multiplies cells Cell division is essential to all life o Enables multicellular organisms to grow to adult size o Replaces worn out or damaged cells o Keep total number of cells constant Some cells are not reproduced o Cardiac muscle cells o Brain cells Cell Cycle o Interphase growing stage 90 of the cell s time in the cycle G1 first gap S synthesis DNA is replicated G2 second gap Makes more cytoplasm Increase protein supply Duplicates all cytoplasmic organelles o Mitotic Phase actual cell division 10 of the cell s time in the cycle Mitosis Nucleus and its components are duplicated and divided Cytokinesis Divides the cytoplasm 8 5 Cell division is a continuum of dynamic changes Mitosis o Prophase o Prometaphase o Metaphase o Anaphase o Telophase Mitotic spindle a football shaped structure of microtubules that guides the separation of the two sets of daughter chromosomes o Centrosomes clouds of cytoplasmic material that in animal cells contain pairs of centrioles Also known as microtubule organizing centers 8 6 Cytokinesis differs for plant and animal cells Cytokinesis division of the cytoplasm occurs during telophase o In animal cells Cleavage Cleavage furrow slight indention in the cell surface Cytoplasm has ring of microfilaments associate with myosin molecules Contraction of myosin and the cleavage furrow deepens causing the cell to pinch into two daughter cells o In plant cells During telophase vesicles containing cell wall material meet at the center of the cell The vesicles fuse to the membranous disk called the cell plate Cell plate grows outward and accumulates more material Membrane of the cell plate fuses with the plasma membrane and create two daughter cells 8 7 Anchorage cell density and chemical growth factors affect cell division Growth factor protein secreted to stimulate cell division o Examples Platelet derived growth factor promotes connective tissue development after an injury Vascular endothelial growth factor promotes blood vessels development during fetal development and injury Density dependent inhibition crowded cells stop dividing o If cells are removed dividing begins again Physical cell surface contact triggers Anchorage dependence must be in contact with a solid surface to divide o Example culture dish 8 8 Growth factors signal cell cycle control system The cell control system operates as a trigger and the coordinator of key events in the cell cycle o It does not occur automatically o Three major checkpoints During G1 During G2 In M phase o Intercellular signals allow the cell cycle to proceed if everything checks out o Retrieves signals from outside of the cell about conditions and other cells o G0 permanently nondividing stage o Signal transduction pathway series of protein molecules convey a message signals changes induced on the next molecule o All proteins are NOT located in the same location 8 9 Growing out of control cancer cells produce malignant tumors Cancer is a disease of the cell cycle o These cells do not give off the normal signals o The divide excessively and invade other cells Transformation the process in which a normal cell is converted into a cancer cell o One mutation in the genes o Tumor abnormal growing mass of body cells Benign tumor cells remain at the original site Do not cause problems unless they grow into other organs May be removed by surgery Malignant tumor spread to other cells and disrupt their function Metastasis the spread of cancer Types o Carcinoma originate on the external or internal coverings of organs o Sarcoma originate in tissues that support the body o Leukemia and lymphoma cancers of blood forming tissues Localized tumors may be surgically removed Radiation slows down the spreading of cancer o Sterility can be a side effect of radiation exposure on the reproductive organs Chemotheraphy o Side effects nausea hair loss Mitosis provides for growth cell replacement and asexual reproduction Chromosomes are matched in homologous pairs Somatic cells body cells Homologous pairs two chromosomes that create a matching pair and code for the same inheritance or gene type o Locus particular location on a chromosome 23 Chromosomes o First 22 autosomal o 23th sex chromosomes determine a person s sex Males XY Females XX Gametes have a single set of chromosomes Life cycle the sequence of stages leading from adults of one generations to the adults of the next o Two sets of