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BIO 325 September 5th Lecture Notes

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University of Texas at Austin
BIO 325
Sanghamitra Mohanty

9/5 Lecture Thursday, September 05, 2013 3:28 PM Chapter 2 Mitosis and Meiosis: Mitosis and meiosis continues the genetic continuity in eukaryotes! Three events that happen in both of mitosis and meiosis 1. Copy of DNA 2. Copies separate 3. Cells divide Mitosis ----- 2 daughter cells produced (same # of chromosomes) Leads to production of gametes with same number of chromosomes as the parent cell  Meiosis ----- chromosomes are halved in daughter cells Eukaryotes - transmission of genetic material from one generation of cells to the next involves MITOSIS AND MEIOSIS *difference b/w eukaryotes and prokaryotes ---- eukaryotes has a nucleus ALL CELLS HAVE: plasma membrane, DNA, and ribosomes Prokaryotes Eukaryotes Nucleoid nucleus No membrane has membranes 1-10 um 10-100 um Chromosome is singular and circular chromosome is linear and multiple No histones histone associated with DNA Spatially and temporarily (in eukaryotes) Spatially - distance Temporally - time distance Cell structure: Nucleolus - ribosomes and RNA are located here Chromatin - in a resting cell, very fine structures all over the nucleus which helps form chromosomes Endoplasmic reticulum - 2 types  Rough ---- has ribosomes all over its surfaces  Smooth ---- doesn't have ribosomes on its surfaces; responsible for lipid synthesis Golgi body - proteins are modified Mitochondria - responsible for ATP synthesis Centriole - present in mitosis and meiosis that moves to opposite poles for division Cell envelope Plasma membrane - selectively allows molecules to get in and out (selectively permeable) Cell wall - plant and bacterial cells have this composed mainly of cellulose and peptidoglycan, respectively Cell coat - expresses certain proteins or molecular markers  Blood type antigen o ABO blood group of your RBCs o For blood transfusion  MHC (major histocompatibility complex)/HLA (human leukocyte antigen) o Every other cells besides RBCs o Very rare to have 2 humans having the exact same MHC  So you don't need to be 100% compatible to get organ transplant or blood transfusion  GENETICALLY CONTROLLED! There are 2 organelles that proved about the endosymbiosis theory: mitochondria and chloroplasts  The organelle's DNA is circular  Enzymes o Transcription and translation  Another major evidence: mitochondria are almost identical to proteobacteria o Chloroplast similar to cyanobacteria Major characteristics of a pair of chromosome: Euchromatin - less densely compacted  Contains all the active genes  Less stained Heterochromatin - very densely compacted  More dense stains  Contains parts of the genome that is nonfunctional  No changes in the inactive genes [CONSERVED through evolution] Homologous pair = biparental inheritance (one from mother + one from father) X and Y has homologous reagents to where they can still come together and perform functions (in males) Different parts of a chromosome: Centromere - constriction present on the chromosome; spindles will attach here during cell division; has heterochromatin Telomeres - has heterochromatin; in each cycle, it gets shorter and shorter  Reaches the point of Hayflick point [telomeres becomes very short; named after the scientist who discovered it] o Cells get the signals the those old telomeres needs to die -------- THEY AGE  The more aging, the more mutations --> can become a malignant situation  Has a role in cancer o Enzyme called telomerase  Stem cells aren't allowed to die, so this enzyme adds to the telomerase to fill in the gap  Only active in stem cells  Cancer cells develop when the genes are overexpressed Euchromatin DESIGNATION: [MEMORIZEEEEEEEEEEE] This is important because tit's one of the signs that shows CANCER! MITOSIS: Karyokinesis - highly regulated, always have equality; separation of chromosomes Cytokinesis - isn't as regulated, so mostly unequal; separation of cytoplasm Interphase - G1, S, and G2  G1 phase ---- adapting to the environment, doing nothing  G0 phase --- metabolically active, surviving, but aren't dividing; will wait until they receive the growth signal o In cancer cells, there is NO G0 PHASE o If pulled out, it's withdrawn from the cell cycle  After G1 phase, cell size will increase  S phase ---- DNA will be copied  G2 phase --- preparation for cell division  Takes up 15 of the 16 hours of dividing cells! Mitosis - splitting of daughter cells  Prophase ---- takes up the most time at 38 minutes o 2 important events  The centrioles move to the opposite poles  Chromosomes become condensed and visible  Prometaphase o
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