Unit 4 –Reproduction and Genetics Lesson 13 - Gamete Production Colorado Agriscience Curriculum

Unit 4, Lesson 13 - Gamete Production 2

3 I: Production of Gametes A) GametogenesisA) Gametogenesis –1. Ovaries produce ova a) Oogenesisa) Oogenesis –2. Testicles produce sperm a) Spermatogenesisa) 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 speciesa) Special cell division in which each new gamete(cell) carries only 1/2 the # of chromosomes a typical cell would in that species

Unit 4, Lesson 13 - Gamete Production 4 I: Production of Gametes B) Initial steps are similar between male and femaleB) Initial steps are similar between male and female –1. Chromosomes replicate a) Each is doubleda) Each is doubled –2. Each pair comes together very accurately (synapsis) a) Now called a primary oocyte ora) Now called a primary oocyte or b) Primary spermatocyteb) Primary spermatocyte

Unit 4, Lesson 13 - Gamete Production 5 II. Spermatogenesis A. Primary SpermatocyteA. Primary Spermatocyte –1. Contains 2 pair of chromosomes a) Two bodies containing 4 structuresa) Two bodies containing 4 structures –2 rapid cell divisions produce 4 cells a) Each ontain 2 chromosomesa) Each ontain 2 chromosomes b) Spermatid cells lose much of their cytoplasm & develop a tailb) Spermatid cells lose much of their cytoplasm & develop a tail

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7 III: OOGENESIS A. 1 st maturation divisionA. 1 st maturation division –1. Produce 1 large oocyte (secondary) & 1 small (1 st Polar Body) a) Unequal size results from body wanting one rich in the expense of the othera) Unequal size results from body wanting one rich in the expense of the other B. 2 nd maturation divisionB. 2 nd maturation division –1. Produces the ovum a) Polar bodies may divide but will soon die and be reabsorbed by the bodya) Polar bodies may divide but will soon die and be reabsorbed by the body

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9 IV: Fertilization A) Fertilization is the union of sperm and ovum and the establishment of paired chromosomesA) 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 dama) 1 member of each pair came from the sire and 1 from the dam

Unit 4, Lesson 13 - Gamete Production 10 IV: Fertilization B) Gametes have only one member of each pair.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 diversitya) This insures genetic diversity

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