Life Sciences Term 1

Gametogenesis

Spermatogenesis

• The germinal epithelium undergoes meiosis
  
• Producing 4 haploid spermatids
  
• Mature to form a spermatozoon
  
• Each spermatozoon is made of a head, middle portion and a tail
  

• The head is mainly made up of the nucleus containing 22 autosomes and either an X or Y gonosome
  
• The middle piece is made up of numerous mitochondria to provide energy for locomotion. The mitochondria contain mitochondrial DNA
  
• The long tail enables the sperm to swim.
  

Oogenesis

• Refers to the process by which ova are produced from the germinal epithelium of the ovaries
  
• At puberty the germinal epithelial of the ovary starts to produce ova by meiosis
  
• One cell inside a follicle undergoes meiosis
  
• 4 haploid cells formed
  
• 3 cells break up; one cell matures into the ovum.
  

• Consists of a haploid nucleus, surrounded by cytoplasm
  
• The nucleus bears the genetic material from the mother while the cytoplasm serves as nutritive material to nourish the future zygote
  
• The ovum is enclosed in a vitelline membrane
  
• One ovum is produced and released every 28 days. It is produced by meiosis and therefore has 22 autosomes (single chromosomes) and an X gonosome
  
• The ovum in the fallopian tube: