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Gamete Devloment
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Gamete Devloment

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  • 1. Gamete Development Differs in Males and Females
  • 2. Spermatogenesis
    • Spermatogenesis is the production of mature sperm cells.
    • Full sperm development occurs in the testes and usually takes about two months for full development.
    • The male ejaculate contains 100 – 200 million sperm.
    • This process begins at puberty and continues until death.
  • 3.  
  • 4.  
  • 5. Oogenesis
    • The production of a mature egg characterized by an unequal cytokinesis.
  • 6.
    • At birth, all primary oocytes for life are present in the body (at least 400,000)
    • The primary oocytes are ‘frozen’ before they have the chance to complete meiosis .
    • When a girl goes through puberty, hormones are made that stimulate one ‘frozen’ oocyte (at a rate of 1 per month) to continue meiosis. IF a sperm is present, meiosis will be completed and the sperm will fertilize the new egg.
    • [Fertilization triggers meiosis to be completed.]
  • 7.  
  • 8.
    • The cycle continues from puberty until menopause.
    • How many eggs does a woman need?
    • 12 per year for how many years…
    • 35-40 years (at the most) = 420-480 eggs and she starts with 400,000…
    • The age of the egg = the age of the woman
  • 9. Spermatogenesis and Oogenesis
    • Spermatogenesis
    • Involves meiosis
    • Produces 4 haploid daughter cells
    • Each daughter cell develops into a sperm
    • Process begins at puberty (sperm are all ‘fresh’)
    • Process ends at death
    • Billions are produced at a time.
    • Oogenesis
    • Involves meiosis
    • Can produce 4 haploid daughter cells
    • One daughter cell becomes the egg; three polar bodies die
    • Process begins before birth (eggs are as old as the female)
    • Process ends at menopause
    • One egg matures monthly.
  • 10.  
  • 11. When can a woman get pregnant?
    • The egg is viable for 12-24 hours after it has left the ovary (ovulation)
    • The sperm is viable for up to 72 hours (although most sperm retain their fertilizing power only for 12 to 48 hours after ejaculation.)
    • The ‘window of opportunity’ for fertilization – 72 hours prior to ovulation to 24 hours after ovulation. This equates to only 3 to 4 days a month.
  • 12.  
  • 13.  

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