Unit 4

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Unit 4 Reproduction and Genetics Lesson 13 -
Gamete Production

• Colorado Agriscience Curriculum

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I Production of Gametes

• A) Gametogenesis
• 1. Ovaries produce ova
• a) Oogenesis
• 2. Testicles produce sperm
• a) Spermatogenesis
• 3. Sex cells divide by meiosis
• a) Special cell division in which each new
  gamete(cell) carries only 1/2 the of
  chromosomes a typical cell would in that species

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I Production of Gametes

• B) Initial steps are similar between male and
  female
• 1. Chromosomes replicate
• a) Each is doubled
• 2. Each pair comes together very accurately
  (synapsis)
• a) Now called a primary oocyte or
• b) Primary spermatocyte

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II. Spermatogenesis

• A. Primary Spermatocyte
• 1. Contains 2 pair of chromosomes
• a) Two bodies containing 4 structures
• 2 rapid cell divisions produce 4 cells
• a) Each ontain 2 chromosomes
• b) Spermatid cells lose much of their cytoplasm
  develop a tail

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III OOGENESIS

• A. 1st maturation division
• 1. Produce 1 large oocyte (secondary) 1 small
  (1st Polar Body)
• a) Unequal size results from body wanting one
  rich in nutrients _at_ the expense of the other
• B. 2nd maturation division
• 1. Produces the ovum
• a) Polar bodies may divide but will soon die and
  be reabsorbed by the body

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IV Fertilization

• A) Fertilization is the union of sperm and ovum
  and the establishment of paired chromosomes
• 1. Zygote is a diploid (Double) because
  chromosomes are in pairs
• a) 1 member of each pair came from the sire and 1
  from the dam

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IV Fertilization

• B) Gametes have only one member of each pair.
• 1. Haploid (Half)
• 2. Gametogenesis reduces the of chromosomes in
  a cell to 1/2 the diploid
• 3. Each gamete carries a random sampling 1/2 of
  each parents genetic code.
• 4. Which sperm fertilizes the ovum is also random
  
• a) This insures genetic diversity

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