Download
gamete maturation n.
Skip this Video
Loading SlideShow in 5 Seconds..
Gamete Maturation PowerPoint Presentation
Download Presentation
Gamete Maturation

Gamete Maturation

383 Vues Download Presentation
Télécharger la présentation

Gamete Maturation

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Gamete Maturation Chapter 3: Meiosis & Development 3.3: Gamete Maturation

  2. How do sperm form? • Spermatogenesis- formation of sperm cells • Begins in testes with diploid stem cells called spermatogonia • Spermatogonia will divide into two daughter cells, one will stay in the stem cell niche and the other will begin process of spermatogenesis

  3. How do sperm form? • Spermatogonium accumulates cytoplasm & replicates DNA • Becomes diploid primary spermatocyte • Primary spermatocyte undergoes meiosis I and forms 2 equal sized haploid secondary spermatocytes

  4. How do sperm form? • Secondary spermatocytes undergo meiosis II and divide to form 4 equal sized haploid spermatids. • Spermatids will grow flagellum and become spermatozoa a.k.a. sperm cells

  5. What are the anatomical structures of a sperm? 3 Body Regions • Head- • Nucleus- holds DNA (23 chromosomes) • Acrosome- cap at the front end of sperm that holds enzymes that will be used to penetrate the egg. • Midpiece- has spiral mitochondria which provides energy for swimming • Tail- flagellum for movement

  6. How do eggs form? • Oogenesis- formation of egg cells • Begins in ovary with diploid stem cells called Oogonia • Each oogonium is surrounded by a follicle cell • A woman is born with all oogonia she is ever going to have.

  7. How do eggs form? • Oogoniumaccumulates cytoplasm & replicates DNA • Becomes diploid primary oocyte • Primary oocyte undergoes meiosis I and forms 2 unequal sized haploid cells: • First Polar Body- small cell with very little cytoplasm • Secondary oocyte- larger cell that will go on to meiosis II

  8. How do eggs form? • First Polar Body can have 2 fates: • Decompose & die • Divide & become second polar bodies which will be absorbed by body • Secondary oocyte divides unequally again in meiosis II and forms: • Second polar body- small cell with little cytoplasm that is absorbed by body • Ovum- egg cell with large volume of cytoplasm • This happens once a month after puberty starts

  9. What happens if a sperm fertilizes a polar body? • Very rare • Body responds as if pregnant • Cell division is unorganized- not considered an embryo • Body causes miscarriage called “blighted ovum”

  10. In females: In ovaries Produces: 1 mature egg, 3 polar bodies which break down Women born with all eggs they will have. Egg is much larger Have all X chromosomes Has no method of movement In males: In testes Produces:4 mature sperm Males begin to produce sperm after puberty, produced constantly until death Much smaller than egg May have X or Y chromosomes Have flagella to move Summary of gametogenesis in males vs. females