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2012-04-30 03:16:58

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  1. Spermatogenesis
    • MOST differentiated cell in body
    • Spermatogonia undergo MITOTIC DIVISIONS
    • First Meiotic division: 2ndary spermatocytes form (spermatocytogenesis)
    • 2nd Meiotic division: haploid spermatids (spermatidogenesis)
    • Spermatids elongate, shedding much of cytoplasm until mature SPERMATOZOA formed (spermiogenesis)
  2. Role of Pou5f1 and Gfra1
    • De-differentiation of germ cells into embryonic germ cells
    • Needs to be SUPPRESSED for progression of sperm
  3. TSA binding
    • Binds to HDAC and KDM1, blocking their activation
    • This results in Pou5f1 activity – allows for chromatin to bind to transcription factors: UPregulation of methylation of H3K4 and
    • DOWNregulation of H3K9 methylation
    • This results in Gfra1 activity – increased expression:
    • UPregulation of H3K9 acetylation
  4. Role of histone modification in spermatogenesis
    Spermatogonia suppression of Pou5f1 and Gfra1 due to: H3K4 acetylation and methylation
  5. Oogenesis
Each oogenesis produces 1 Ovum
    1 ovum contains bulk of cytoplasmic material
  6. 2 Mechanisms of asymmetric division
    • SPINDLE is very important in both
    • 1. An eccentrically located spindle allows for cell division of two different sized cells
    • 2. Axis of polarity is established in cell, along which division spindle is established. After cell division, two daughter cells result with different contents
  7. Role of minimizing size of polar body
    • To avoid any competition b/w two daughter cells for FERTILIZATION
    • Polar body has reduced surface and no microvillisities for sperm to bind
  8. Role of Formin 2
    • Microfilament binding protein
    • Aid in Directing formation of Straight ACTIN MICROfilaments
    • Helping in spindle migration and chromosomes transfer to cortex
    • Confirmed from work that shows mouse oocytes do NOT have astral microtubules for connecting the spindles to the cortex and migration of chromosome