BOLOGY 107 Lecture 20Outline of Last Lecture I. CytokinesisII. Cell Cycle ControlIII. Meiosis Outline of Current Lecture IV. Genetic VariationV. Variation in Cell Replicationa. Spermatogenesis b. OogenesisVI. Cell CommunicationCurrent LectureGenetic Variation1) Allows for a wider variety in a species2) Occurs though:a) Crossing over in prophase I of meiosis b) Independent assortment in metaphase Ic) Random fertilizationVariation in cell replication3) Many fungi do not perform cytokinesis after mitosis4) Spermatogenesis a) Sperm do not undergo full cytokinesis until maturation5) Oogenesis a) Eggs undergo asymmetric cytokinesis with two pausesi) Eggs get through prophase I while the female is in the womb, undergo meiotic arrest until pubertyii) Start of menstrual cycle is the remainder of meiosis I iii) The egg divides unequally to keep the egg and form the polar body during ovulation, undergo meiotic II arrestiv) Once fertilized, meiosis is continued and another polar body is formedv) Both polar bodies die ofCell CommunicationThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.6) Direct contacta) Gap junctions of plasmodesmatab) Cell-cell recognition through membrane proteins over long or short distances7) Without contacta) Pancrine- signal nearby cellsb) Autocrine- cell signals itselfc) Endocrine- distant communication via circulation, usually hormones8) Signal pathwaysa) Reception i) Protein, usually on the membrane, detects signal, changes shape(1) Examples: channel proteins(2) Exception: steroids and nitric oxide just pass through the membrane themselvesb) Signal transductioni) Change in the protein relays to others, molecule transduction(1) Known as second messenger(2) Allows for amplification of signal(3) Example: kinase cascadec) Response i) Target receives signal, changes behavior(1) Main targets:(a) Gene regulation production(b) Activity
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