Set 2 of Unit 4 Notes
Set 2 of Unit 4 Notes Bio 190
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This 7 page Class Notes was uploaded by Danielle Francy on Thursday April 14, 2016. The Class Notes belongs to Bio 190 at Towson University taught by Joseph Velenovsky in Fall 2015. Since its upload, it has received 4 views. For similar materials see Intro Biology for Health Professions in Biology at Towson University.
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Date Created: 04/14/16
Unit 4 Notes Metaphase: ● ***Mitotic spindle fully formed and functional ● Poles are completely at opposite ends of the cell ● Chromosomes converge on the metaphase plate ● Metaphase plate is an imaginary area equidistant between the two ends of the spindle ● Centromeres are lined up on the metaphase plate ● Within each chromosome, the kinetochores face opposite poles ● Microtubules attached to a particular chromatid are from one pole; its sister Anaphase: ● Sister chromatids are separated as the two centromeres of each chromosome come apart ● Upon this separation, each sister chromatid is labeled a daughter chromosome ● Kinesins and Dynein walk daughter chromosomes centromere first along microtubule towards opposite poles of the dividing cell ● At the same time, spindle microtubules attached to kinetochores shorten ● Spindle microtubules not attached to kinetochores lengthen ● Poles are moved farther apart Telophase: ● Cellular expansion or elongation that started in anaphase continues ● Daughter nuclei appear at opposite ends of the cell ● Nuclear envelopes form around the chromosomes at each pole ● Telophase is reverse of prophase ● Chromatin structure starting ● Presence of a nuclear envelope ● Shrinking of the mitotic spindle ● By the end of telophase, chromosomes are nearly coiled as chromatin ● Mitotic spindle has disappeared ● Mitosis is complete after telophase ● Defined as the equal division of one nucleus into two genetically identical daughter nuclei ● Still undergo cytokinesis ● Cytokinesis occurs often concurrently with telophase Cytokinesis: ● Two daughter cells completely separate after the end of mitosis ● Begins concurrently with telophase ● Animal and plant cells undergo cytokinesis differently Cell Walls in Plant Cells: ● Process called cleavage ● First sign of cleavage is the cleavage furrow ● Shallow indentation ● Ring of microfilaments made of Actin ● Associated with myosin ● Interacting causes contractions ● Cleavage furrow deepens and eventually splits the parent cell into two distinct daughter cells ● Cytokinesis is the division of the cytoplasm; the division of the nucleus is associated with mitosis ● During telophase, vesicles containing cell wall material (cellulose, etc.) ● Gather at the middle of the parent cell ● Vesicles fuse forming a membranous disk called the cell plate ● Cell plate grows outward adding more cell wall material from vesicle fusion ● Eventually, the cell plate fuses with the plasma membrane ● Cell plate’s contents join the parental cell wall ● Two daughter cells ● Control of timing of cell division is important ● Skin cells vs. liver cells ● Mammalian cells ● Growth factors ● Essential nutrients ● Secreted protein that stimulates other cells to divide ● Platelet derived growth factor ● Injury to skin ● Blood platelets release growth factor ● Rapid growth of connective cell tissue to seal the wound ● Vascular endothelial growth factor (VEGF) ● Stimulates new blood vessels during fetal development and after injury ● VEGF production Physical factors: ● Densitydependent inhibition ● Crowded cells stop division ● Animal cells form single layer ● When space is filled and contact occurs between cells, division stops ● If cells are removed, space fills again ● Cellsurfaced proteins between adjacent cells touch ● Inhibition of cell division ● Anchorage dependence; animal cells ● Must be in contact with solid surface to divide ● Culture dish; ECM Animal Cells: ● Normally anchored in a fixed position ● Nutrients supplied by blood ● Usually don’t divide unless signaled by other cells ● Growth factors ● Cell cycle controlled by control system ● Cyclins and cyclin dependent kinases ● Controls progression of cell cycle ● Progression is not automatic ● Proteins of the control system determine progression Checkpoints: ● Critical ● Need specific signals ● G1, G2, M ● Progress cell cycle ● Stop progression ● Intracellular signals ● Extracellular signals ● Detected by control system determine if progression should occur ● Key cellular processes ● Environmental conditions outside the cell ● First gap checkpoint is the most important ● If signal never arrives, switch to G0 ● Mature muscle cells ● Control system at G1 checkpoint ● Growth factor ● Changes in each protein molecule ● Ex: phosphorylation ● Cyclins, etc. not located in one place, but throughout cell ● Signals can override the brakes ● Progression through cell cycle Disease of the Cell Cycle: ● Mutation in one or more genes for proteins in control system ● Immune system destruction ● Evasion ● Benign tumor ● Malignant tumor ● Spreads to other tissues ● Cancer ● Metastasis ● Carcinomas ● External/internal coverings ● Intestinal lining ● Skin ● Sarcomas supporting tissues ● Bone muscle, leukemias, lymphomas, blood forming tissues, bone marrow, spleen, lymph nodes ● Loss of cell cycle control ● Not influenced by normal signals ● Proceed through checkpoints even if growth factors not present ● Can synthesize growth factors themselves ● If they do stop dividing (IF) it is random not at checkpoints ● Immortal as long as nutrients present ● Normal mammalian cells stop after 2050 times ● Local tumors removed surgically ● Radiation damages DNA ● Cancer cells rather than normal cells ideally ● Cancer cells hypothesized to have lost ability to repair DNA damage (all they do is divide) Normal Cells Side Effects: ● Radiation can cause sterility ● Metastatic tumorschemotherapy ● Drugs disrupt specific steps in the cell cycle ● Taxol freezes the mitotic spindle after it forms ● Stop division at metaphase ● Vinblastin ● Prevents mitotic spindle formation entirely Side effects: ● Effects on normal cells that rapidly divide ● Intestinal cells, nausea, hair loss, hair follicle cells, immune cells ● Susceptibility to infection ● Differential selective gene expression in response to both internal and external signals ● Turn genes on and off ● Multicellular eukaryotes require cellular differentiation ● Specialized in structure and function Chromosomes: ● Tightly packaged DNA ● Found only during cell division ● DNA is not being used for macromolecule synthesis Chromatin: ● Unwound DNA ● Found throughout interphase ● DNA is being used for macromolecule synthesis Somatic Cells: ● Body cells ● 46 chromosomes ● Metaphase of mitosis ● 2 sister chromatids ● Arranged into matching pairs based primarily on size ● Centromere position ● Banding pattern ● 23 pairs of duplicated chromosomes ● Homologous chromosomes ● Homologs ● Genes are located at the same loci ● Allelic versions may be different ● Locus, banding patterns ● In females, 46 chromosomes are arranged neatly into 23 pairs of homologous chromosomes ● In males, X and Y (partly homologous) ● Determine sex and other functions ● Autosomes Human Life Cycle: ● Two sets of chromosomes in each person; one from mother and one from father ● Species that reproduce sexually, share this characteristic with humans ● Diploid ● Somatic cells contain pairs of homologous chromosomes ● Total number is diploid number (2n) ● Humans diploid number = 46 ● 2n = 46 ● Gametes= egg and sperm ● Single set of chromosomes ● 22 autosomes ● 1 sex chromosome ● Either X or Y ● All eggs have X ● Sperm determines sex of offspring ● Haploid cells ● One chromosome of each homologous pair ● Homologous number = 23 ● N = 23 ● Haploid sperm, haploid egg ● Fertilized egg ● Fertilization ● Zygote ● Two sets of homologous chromosomes ● Diploid ● One set from each parent ● Development occurs Sexual Reproducing Organisms: ● Alternation of diploid and haploid stages ● Good mechanism because gametes (haploid) prevent chromosome number from doubling every generation ● Produced by meiosis ● Only in reproductive organs ● Testes and ovaries in humans ● Mitosis produces daughter cells with same number of chromosomes ● ***Meiosis reduces the chromosome number by half ● Duplication during interphase ● Separate haploid daughter cells ● Still doubled ● Separation of sister chromatids ● Four daughter cells are haploid ● Only a single chromosome from parental homologous pair ● Haploid gametes in diploid organisms ● Two haploid gametes combine ● Restoration of diploid state ● Prevents doubling of genetic material each generation ● Before meiosis, just like mitosis, chromosomes duplicate ● Meiosis I, Meiosis II ● Two rounds of cellular division ● Four daughter haploid cells ● Inherited ● ***Prophase I and crossing over ● Similar to mitosis Interphase: ● Chromosomes duplicate ● Each chromosome consists of two genetically identical sister chromatids ● Centrosome has also duplicated ● By the end of interphase ● Early prophase I ● Chromatin coils up ● Individual chromosomes are visible ● Synapsis ● Homologous chromosomes (each made of 2 sister chromatids) are paired ● Four chromatids tetrad