Biology investigatory project on Gametogenesis

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Biology investigatory project on Gametogenesis for Class 12 cbse
  CONTENTS SPERMATOGENESIS 1) Location 2) Duration 3) Stages a) Speramtocytogenesis  b) Spermatidogenesis c) Spermiogenesis 4) Role of Sertoli cells 5) Influencing Factors 6)Harmonal control OOGENESIS 1) Oogenesis in Humans 1.1   The creation of oogonia 2)Human oogenesis 2.1.Oocytogenesis 2.1.1.Number of primary oocytes 2.2 Ootidogenesis 2.2.1 Meiosis I 2.2.2 Meiosis II 2.2.3 Folliculogenesis 2.3. Maturation into ovum 2.4.In vitro maturation Bibliography   Spermatogenesis Spermatogenesis  is the process in which spematozoa are produced from male primordial germ cells by way of mitosis and meiosis. The initial cells in this pathway are called spematogonia, which yield primary spermatocytes by mitosis. The primary spermatocyte divides meiotically into two secondary spermatocytes; each secondary spermatocyte then completes meiosis as it divides into two spermatids. These develop into mature spermatozoa, also known as sperm cells. Thus, the primary spermatocyte gives rise to two cells, the secondary spermatocytes, and the two secondary spermatocytes by their subdivision produce four spermatozoa. Spermatozoa are the mature male gametes in many sexually reproducing organisms. Thus, spermatogenesis is the male version of gametogenesis. In mammals it occurs in the male testes and epididymis in a stepwise fashion. Spermatogenesis is highly dependent upon optimal conditions for the process to occur correctly, and is essential for sexual reproduction. DNA methylation and histone modification have been implicated in the regulation of this process. It starts at puberty and usually continues uninterrupted until death, although a slight decrease can be discerned in the quantity of produced sperm with increase in age (see Male infertility).      Spermatogenesis produces mature male gametes, commonly called sperm   but specifically known as spermatozoa  , which are able to fertilize the counterpart female gamete, the oocyte, during conception to produce a single-celled individual known as a zygote. This is the cornerstone of sexual reproduction and involves the two gametes both contributing half the normal set of haploid chromosomes to result in a chromosomally normal diploid zygote. To preserve the number of chromosomes in the offspring –  which differs between species –  each gamete must have half the usual number of chromosomes present in other body cells. Otherwise, the offspring will have twice the normal number of chromosomes, and serious abnormalities may result. In humans, chromosomal abnormalities arising from incorrect spermatogenesis can result in Down syndrome, Klinefelter’s syndrome, an d spontaneous abortion Location Spermatogenesis takes place within several structures of the male reproductive system. The initial stages occur within the testes and progress to the epididymis where the developing gametes mature and are stored until ejaculation. The seminiferous tubules of the testes are the starting point for the process, where stem cells adjacent to the inner tubule wall divide in a centripetal direction — beginning at the  walls and proceeding into the innermost part, or lumen  — to produce immature sperm. Maturation occurs in the epididymis .  
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