Meeting Gametes

Meeting Gametes

Study the following details for a better understanding of gametogenesis and what happens after it.

1. Process and location
   
   • Male - Spermatogenesis in the testes.
   • Female - Oogenesis in the ovaries.
2. Parent cell for gametogenesis
   
   • Male - Primary spermatocyte.
   • Female - Primary oocyte.
3. Cell produced after Meiosis I
   
   • Male - Two secondary spermatocytes.
   • Female - One secondary oocyte (X) and one (1st) polar body (Y).
4. Cell produced after Meiosis II
   
   • Male - Four spermatids.
   • Female -
     
     • From the secondary oocyte (X): One ovum + One polar body.
     • From the first polar body (Y): Two other polar bodies.
5. What happens to cells produced after Meiosis II?
   
   • Male - Spermatids differentiate into sperms.
   • Female - All three polar bodies will degenerate; only the ovum will survive.
6. When does Meiosis II occur?
   
   • Male - Immediately after Meiosis I.
   • Female -
     
     • For the first polar body: immediately after Meiosis I.
     • For the second oocyte: only after a sperm penetrates the oocyte.
7. What happens during sexual intercourse?
   
   • Male - Sperms are ejaculated from a male's penis into a female's vagina.
   • Female - Sperm from a male swim upwards, from a female's vagina, through the cervix, into the uterus and then to the Fallopian tubes.
8. Site for fertilisation
   
   • Male - none.
   • Female - In the Fallopian tubes of the female reproductive system.
9. Product of fertilisation
   
   • Male - none.
   • Female - A diploid zygote (containing 46 chromosomes), which then develops into an embryo.

What happens after sexual intercourse?

• Possibility I
  
  • A sperm meets the secondary oocyte and penetrates it.
  • Meiosis II quickly occurs in the secondary oocyte, and an ovum and a polar body is formed.
  • The polar body degenerates.
  • The nucleus of the ovum fuses with the nucleus of the sperm.
  • Fertilisation is successful and a diploid zygote is formed.
  • The female is pregnant.
    
• Possibility II
  
  • None of the sperms meet the secondary oocyte. This could mean ovulation has
    
    • not occurred yet;
    • occurred but the secondary oocyte, which can only live for 24 hours, has died.
      
  • No fertilisation occurs.
  • No zygote is formed.
  • The female is not pregnant; she gets her next period as usual.