Unit 4 –Reproduction and Genetics Unit 4 –Reproduction and Genetics

Lesson 13 - Gamete ProductionLesson 13 - Gamete Production

Colorado Agriscience Colorado Agriscience CurriculumCurriculum

Unit 4, Lesson 13 - Gamete Production 2

Unit 4, Lesson 13 - Gamete Production 3

I: Production of GametesI: Production of Gametes

• A) Gametogenesis A) Gametogenesis – 1. Ovaries produce ova1. Ovaries produce ova

• a) Oogenesis a) Oogenesis

– 2. Testicles produce sperm 2. Testicles produce sperm • a) Spermatogenesis a) Spermatogenesis

– 3. Sex cells divide by meiosis 3. Sex cells divide by meiosis • a) Special cell division in which each new a) Special cell division in which each new

gamete(cell) carries only 1/2 the # of gamete(cell) carries only 1/2 the # of chromosomes a typical cell would in that species chromosomes a typical cell would in that species

Unit 4, Lesson 13 - Gamete Production 4

I: Production of GametesI: Production of Gametes

• B) Initial steps are similar between B) Initial steps are similar between male and femalemale and female– 1. Chromosomes replicate 1. Chromosomes replicate

• a) Each is doubleda) Each is doubled

– 2. Each pair comes together very 2. Each pair comes together very accurately (synapsis) accurately (synapsis) • a) Now called a primary oocyte ora) Now called a primary oocyte or• b) Primary spermatocyte b) Primary spermatocyte

Unit 4, Lesson 13 - Gamete Production 5

II. Spermatogenesis II. Spermatogenesis

• A. Primary SpermatocyteA. Primary Spermatocyte– 1. Contains 2 pair of chromosomes1. Contains 2 pair of chromosomes

• a) Two bodies containing 4 structuresa) Two bodies containing 4 structures

– 2 rapid cell divisions produce 4 cells 2 rapid cell divisions produce 4 cells • a) Each ontain 2 chromosomes a) Each ontain 2 chromosomes • b) Spermatid cells lose much of their b) Spermatid cells lose much of their

cytoplasm & develop a tail cytoplasm & develop a tail

Unit 4, Lesson 13 - Gamete Production 6

Unit 4, Lesson 13 - Gamete Production 7

III: OOGENESIS III: OOGENESIS

• A. 1A. 1stst maturation division maturation division– 1. Produce 1 large oocyte (secondary) & 1 1. Produce 1 large oocyte (secondary) & 1

small (1small (1stst Polar Body) Polar Body)• a) Unequal size results from body wanting one rich a) Unequal size results from body wanting one rich

in nutrients @ the expense of the otherin nutrients @ the expense of the other

• B. 2B. 2ndnd maturation division maturation division– 1. Produces the ovum 1. Produces the ovum

• a) Polar bodies may divide but will soon die and be a) Polar bodies may divide but will soon die and be reabsorbed by the bodyreabsorbed by the body

Unit 4, Lesson 13 - Gamete Production 8

Unit 4, Lesson 13 - Gamete Production 9

IV: FertilizationIV: Fertilization

• A) Fertilization is the union of A) Fertilization is the union of sperm and ovum and the sperm and ovum and the establishment of paired establishment of paired chromosomes chromosomes – 1. Zygote is a diploid (Double) 1. Zygote is a diploid (Double)

because chromosomes are in pairsbecause chromosomes are in pairs• a) 1 member of each pair came from the a) 1 member of each pair came from the

sire and 1 from the damsire and 1 from the dam

Unit 4, Lesson 13 - Gamete Production 1

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IV: FertilizationIV: Fertilization

• B) Gametes have only one member of B) Gametes have only one member of each pair.each pair.– 1. Haploid (Half) 1. Haploid (Half) – 2. Gametogenesis reduces the # of chromosomes in 2. Gametogenesis reduces the # of chromosomes in

a cell to 1/2 the diploid # a cell to 1/2 the diploid # – 3. Each gamete carries a random sampling 1/2 of 3. Each gamete carries a random sampling 1/2 of

each parents genetic code.each parents genetic code.

– 4. Which sperm fertilizes the ovum is also random4. Which sperm fertilizes the ovum is also random • a) This insures genetic diversity a) This insures genetic diversity

Unit 4, Lesson 13 - Gamete Production 1

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