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genetics 2 - Klug Chapter 2 Mitosis and Meiosis I Cell...

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Klug Chapter 2: Mitosis and Meiosis I. Cell structure is closely tied to genetic function A. Cell Boundaries -plasma membrane: outer covering that defines the cell boundary and delimits the cell from its immediate external environment. Actively controls the movement of materials into and out of the cell -cell wall: membrane of plants composed of polysaccharide cellulose -peptidoglycan: major component of bacterial cells. Peptide and sugar units -capsule: another covering of bacteria. Under genetic control -cell coat: covers plasma membrane consisting of glycoproteins and polysaccharides. Provides biochemical identity at the surface of cells -AB and MN antigens: on RBC -histocompatibility antigens: elicit immune response during tissue and organ transplants -receptor molecules: constitute recognition sites that transfer specific chemical signals across the cell membrane in to the cell. B. Nucleus rRNA synthesized at nucleolus and initial stages of ribosomal assembly occur here. -nucleolus organizer region (NOR): areas of DNA encoding rRNA -nucleoid: area where genetic material present as a long circular DNA molecule in bacteria. C. Cytoplasm and Cellular Organelles Has cytoplasm and cytosol and tubules and filaments comprising the cytoskeleton providing a lattice of support structures within the cytoplasm. These tubules consist primariy of tubulin-derived microtubules and actin-derived microfilaments, which maintains cell shape, facilitates ell mobility and anchors the various organelles -ER: compartmentalizes cytoplasm increasing SA. Smooth: synthesizes fatty acids and phospholipids and rough: translation to proteins with mRNA -mitochondria: sites of oxidative phases of cell respiration, creating ATP -chloroplasts: in plants algae and protozoans that photosynthesize Mitochondria and chloroplasts can duplicate themselves and transcribe and translate their genetic information -endosymbiont hypothesis: evolutionary origin of mit and chloror that they established a symbiotic relationship with eukaryotes -centriole: in animals and some plants. Cytoplasmic body in centrosome are associated with organization of spindle fibers that function in mitosis and meiosis -spindle fibers: organized by centrioles occurring during early phases of mitosis and meiosis. Made of microtubules, they are important in mvmt of chromosomes as they separate during cell division. They consist of polymers of polypeptide subunits of tubulin II. Homologous pairs Each have centromere, which establishes the general appearance of each chromosome.
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