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# Gametogenesis: Conversion of cells into gametes ## Gametogenesis - conversion of cells into gametes **Chapter 2** - *Gametogenesis: conversion of cells into gametes in male and female organisms* **Number of Chromosomes:** * __Diploid__ * __Diploid (2x DNA)__ * __Diploid (2x DNA)__ * __D...

# Gametogenesis: Conversion of cells into gametes ## Gametogenesis - conversion of cells into gametes **Chapter 2** - *Gametogenesis: conversion of cells into gametes in male and female organisms* **Number of Chromosomes:** * __Diploid__ * __Diploid (2x DNA)__ * __Diploid (2x DNA)__ * __Diploid (2x DNA)__ * __Tetraploid__ * __Diploid__ **Figure 2-4:** First and second meiotic divisions * **A.** Homologous chromosomes approach each other * **B.** Homologous chromosomes arrange in pairs and each member of the pair contains two chromatids. * **C.** Homologous chromosomes joined together, tightly in pairs exchange parts of their chromatids (crossing over). Note the chiasma * **D.** Chromosomes with double structure separate * **E.** Anaphase of the first meiotic division * **F.** During the second meiotic division, chromosomes with double structure separate at the centromere. After the division, the chromosomes in each of the four daughter cells differ from each other. * **G.** Cells formed after the first meiotic division * **H.** Cells formed after the second meiotic division **Figure 2-5:** Events that occur during the first and second divisions of maturation * **A.** The female germ cell(primary oocyte) gives rise to only one mature gamete, the mature oocyte. * **B.** The male germ cell (primary spermatocyte) gives rise to four spermatids, which become sperm. **Images:** * **A** - Start of pairing. * **B** - Paired chromosomes * **C** - Formation of chiasma * **D** - Separation of the chromosomes of the double structure * **E** - Anaphase of the first meiotic division * **F** - Cells that are formed from the first meiotic division. * **G** - Cells formed from the second meiotic division _Diagram of the processes of meiosis in the primary oocyte:_ * The primary oocyte after DNA duplication * These cells contain 46 chromosomes with double structure * The primary oocyte after the first division of maturation * 23 chromosomes with a double structure * The second division of maturation * 23 simple chromosomes * The mature oocyte (22+X) _Diagram of the processes of meiosis in the primary spermatocyte:_ * The primary spermatocyte after DNA duplication [in mitosis] * The primary spermatocyte after the first division of maturation * 23 chromosomes with a double structure * The second division of maturation * 23 simple chromosomes * 22+X] * The secondary spermatocyte * The spermatid * The bodies of the poles